In November 1983, Gerard McLaughlin and his fiancee Val Cardwell set up home together in a council flat at No 1 Cruikshank Street, Islington, North London.

They were a fortunate couple. Not only was the local authority housing list 12,000 applicants long, but their new place was on a picturesque Georgian terrace.

How had they got so lucky?

The couple had no dependent children or pressing medical problems. Nor had they been Islington residents. Their previous address was in South Wales, 160 miles away. They were not even homeless.

A graduate and former school teacher, McLaughlin owned a house in the Welsh Valleys, from which he was receiving a landlord's rent.

In November 1983, Gerard McLaughlin (pictured during the 1970s) and his fiancee Val Cardwell set up home together in a council flat at No 1 Cruikshank Street, Islington, North London. On November 10, 1983, Derry-born McLaughlin had been released from Maidstone jail

Yet they had jumped to the front of the Islington housing queue.

Having a conviction for IRA-related terrorist activities — or being the partner of a convicted terrorist — didn't feature in Islington Council's 1983 'order of priorities' for housing allocation, which the Mail has found in archives.

But this was the reason Islington ratepayers ended up — unwittingly — providing the pair with a new home.

On November 10, 1983, Derry-born McLaughlin had been released from Maidstone jail, where he had served a four-year sentence for conspiring to cause explosions. He had been caught gathering specialist parts for making radio- controlled bombs, of a type used in scores of IRA attacks, including the fatal blasts in London's Hyde Park in 1982.

He and his fiancee needed somewhere to live outside the Valleys — and quickly.

The close-knit working-class community in the pit villages of Brynmawr, Nantyglo and Blaina had been outraged by his activities in their midst and Cardwell's support for the Provisionals.

A young man from Blaina serving in the Royal Regiment of Wales had been shot dead by the IRA, leaving a widow.

Days after McLaughlin's release, local feeling against the IRA was heightened when Private Andy Bull from Nantyglo was horribly maimed by a bomb while on patrol in Belfast. The son of a Labour-voting miner, he was blinded for life.

Days after McLaughlin's release, local feeling against the IRA was heightened when Private Andy Bull (left and right) from Nantyglo was horribly maimed by a bomb while on patrol in Belfast. The son of a Labour-voting miner, he was blinded for life

But it was McLaughlin, not that young Welshman, who received assistance from a new Labour MP and his hard-Left comrades who had just raised the red flag over Islington town hall.

This is the shocking, untold story of the friendship between Jeremy Corbyn and the convicted terrorist, who in letters from his cell ranted about 'the Jews', applauded IRA atrocities and often signed off ' F*** the Queen'. Later, Corbyn and McLaughlin travelled the world and shared platforms with notorious anti-Semites. 'Jeremy is a good friend,' McLaughlin said in 2015.

The Mail has spoken to scores of actors in this saga and examined thousands of documents in archives across the UK. Our research even took us to Australia, where Andy Bull emigrated having been bullied out of his job at a Labour council after he failed to take part in a union strike.

Bull told us this week: 'It's frightening that Corbyn could be our next Prime Minister. He is unfit to lead this country.'

After reading this two-part investigation, you may well agree.

McLaughlin settled in Nantyglo — Andy Bull's home village — at 16, having been sent there to live with relatives to escape the Troubles back home. He went on to study maths at the University of Wales and then trained as a teacher.

In 1976, he took up a post at Ebbw Vale comprehensive school.

By many accounts he was popular, though his political extremism was evident. He sold the newspaper of the Workers Revolutionary Party and later became the South Wales organiser for Provisional Sinn Fein.

Protest: McLaughlin (left) and Corbyn at a Bloody Sunday 20th anniversary march in 1992

He also started a relationship with Ms Cardwell, having met her when he spoke at her Communist Party branch. Former IRA commander and Sinn Fein President Gerry Adams would later describe her glowingly as a 'lifelong socialist and Irish republican activist'.

When McLaughlin bought a terrace house in Brynmawr, neighbours began to suspect his more clandestine activities.

Malcolm Hoffman had gone to McLaughlin's house to deliver misdirected post. He recalls seeing an IRA magazine on his table. On the cover, Hoffman said, was 'a man wearing a balaclava and clutching an AK-47'.

He added: 'I couldn't believe it. This was a quiet little Welsh mining town.'

It was in 1980 that the events leading to McLaughlin's terrorist involvement took place.

On March 1, Cardwell bought a radio receiver and related equipment in a Cardiff shop. Later that month she tried to buy further radio control parts in Newport.

On each occasion, McLaughlin waited outside. Then they both travelled to Luton and met an alleged IRA member. McLaughlin was arrested the next day.

His trial took place in April 1981. Cardwell was not charged because the Crown Prosecution Service did not believe it could prove she knew what the radio parts would be used for.

The court was told that between 1972 and 1980 there were 140 bomb incidents in Northern Ireland in which the same radio parts were used. McLaughlin denied the charges. He claimed he thought the parts would be smuggled into jails to set up radio links with Provo prisoners.

The Mail has spoken to Joseph Meadows, 78. He was the Special Branch officer who worked on the undercover operation that snared McLaughlin. He said: 'When we searched [his house] we found packaging for a large number of model kits which had been bought as far afield as Leicester.

'They were designed legitimately to be used in kit cars . . . the IRA realised they could use them to trigger bombs remotely. Obviously, each receiver could only be used once for that purpose [which is why McLaughlin bought so many].'

McLaughlin was sentenced to six years imprisonment, reduced to four on appeal.

The judge told him: 'By your crime, you intended to make a substantial and vicious contribution to the appalling violence, death and destruction which is taking place elsewhere by people with whom you have demonstrated a deep sympathy.'

Links: Corbyn and McLaughlin in 2010

The outraged family of McLaughlin's girlfriend, Valerie Cardwell, said they did not speak to her again because of her involvement with McLaughlin and sympathy for the Provos.

Her brother Gwyn, 63, said: 'Feelings around here were running very high, especially with what happened to some of the lads from this area who were serving in Ulster and killed or injured. We made a choice between our sister and her beliefs and the community we lived and worked in.'

Another brother, Linden, said they were not aware she had died in 2011 until informed by others, adding that none of the family attended her funeral. Yet one person who did go to that funeral was Jeremy Corbyn. Gerry Adams, former IRA commander, sent a eulogy to her.

McLaughlin served most of his sentence in Maidstone jail and between July 1981 and September 1983, he sent 26 letters to the organiser of a Left-wing Welsh nationalist group.

We found them in a political archive at the National Library of Wales. When sent, McLaughlin would have expected them to have been vetted by the prison authorities, so would have been circumspect in what he wrote.

Nevertheless, he set out his hatred of Israel and support for IRA violence on the British mainland. Most of the letters signed off with two acronyms. One was 'FTQ!' ('F*** the Queen') the other 'UTP!' ('Up the Provos').

They reveal how his morale improved during imprisonment thanks to the efforts of sympathisers prepared to help him and his girlfriend start a new life. One of them was Jeremy Corbyn.

In a letter dated August 7, 1981, McLaughlin confirmed that thanks to his supporters' help, his mortgage arrears on his Brynmawr home had been cleared and he had rented it out.

But he was concerned about the fury that his activities had caused. There had been an attack on his girlfriend, Cardwell.

McLaughlin wrote from his cell: 'It sickens me that British people can act in such a despicable way and then call the IRA terrorists . . . Val will not be intimidated and neither will any of us until we have won.'

His comrades' ongoing activities made that animosity worse. On October 10, 1981, the IRA detonated another radio remote-controlled bomb, outside Chelsea Barracks in London. Two civilians — a 59-year-old woman and a teenage boy — died in the blast and 40 people were injured. On November 7, McLaughlin wrote in response to his Welsh nationalist correspondent who had expressed concern at the IRA campaign.

'People have to realise that a war does kill innocent people,' McLaughlin argued. 'The British will have to make up their minds — if they want to fight a war in Ireland then they must be prepared to pay that price.'

Despite his hatred of the British state, he had asked the Home Office to pay for him to study for an MA in philosophy. This was refused, but he still wanted to study at Kent University.

In a letter dated July 6, 1982, he wrote: 'I will return to the struggle as soon as they release me. No doubt this is not my last spell in prison.' He signed off 'Utp! Ftq!'

Another incendiary letter was sent on July 31, raging against 'the Jews' and justifying the Hyde Park bombings, which had killed 11 soldiers just days before. Yet another radio remote-controlled device was used in one of the blasts. 'The bombings in London have shown the strength and expertise of the volunteers and also their ability to strike military targets with impunity,' he crowed. Of Israel he said: 'The tragedy of the Zionist final solution to the Palestinian problem recalls the horrors of Nazism itself.

McLaughlin was imprisoned for buying radio parts like the ones used in the 1982 Hyde Park bomb (pictured)

'The fact the Jews were persecuted and butchered by fascists and racists does not give them the right to inflict such treatment on a totally different people.'

His language is remarkably similar to that used by anti-Semites in Mr Corbyn's current circle. On January 16, 1983, McLaughlin again wrote of his girlfriend's welfare. 'I am anxious to find her a place to live away from South Wales. She needs some peace . . . Utp!'

His wishes would soon be answered — and how. Labour's hard-Left was about to seize total control in Islington. A letter in September reported a sudden turn for the better in McLaughlin and Cardwell's fortunes.

The Home Office had rejected a Special Branch application for McLaughlin to be excluded from the British mainland. He had a release date and knew where he would be living. 'Val, my girlfriend, has at last got a flat in London so I will have somewhere to go,' he wrote. 'Val will be moving to London within the next month I think.'

He added: 'I have a few irons in the fire which I shall tell you about when I see you. Nothing mysterious but what the Home Office don't know — the Home Office can't foul up, so it's probably best not to write it in a prison letter. UTP!' These 'irons in the fire' were being heated by comrades in North London.

Jeremy Corbyn first met Valerie and Keith Veness at the Young Socialists annual conference at Skegness in 1972. 'Val' would become his personal assistant in the Commons and worked with him on campaigns related to Irish Republicanism.

They remain friends — indeed, the Venesses still edit the Corbyn-supporting London Labour Briefing. Both revolutionary Marxists, they were crucial figures in Corbyn's rise.

Mrs Veness was elected to Islington Council in 1974. In the 1982 elections, all but one of the council seats went to Labour.

Both Venesses were elected, Val as deputy leader. The 'Loony Left' had taken over and Islington was twinned with the revolutionary Marxist-ruled island of Grenada.

The Red Flag was raised over the town hall and Mrs Veness was quoted as saying it was 'a symbol that the years when Socialism was absent is over'.

Corbyn was a councillor in neighbouring Haringey borough. According to a recent biography, Mrs Veness was the Islington 'power broker' behind his selection as the prospective Labour candidate for Islington North.

Mrs Veness was quoted as saying: 'I might be able to help you. But it's got to be kept secret.'

Eventually, Corbyn would be presented as her preferred candidate. He was duly selected and in the general election of June 1983 became an MP.

Allegations of malpractice and misuse of resources dogged the hard-Left local authority in his constituency. Not least the housing department. In June 1983, Islington Council confirmed it was providing a local authority property to be used as a 'rest house' for women protesting at Greenham Common air base.

That summer, a journalist carried out an undercover investigation into housing allocation.

She posed as a representative of a fictional group called the Islington Women's Cooperative Against State Oppression in Holloway Prison.

Its fake manifesto likened the Islington jail's staff to Nazis — a favourite Corbynista analogy. The journalist said she approached Val Veness, who told her: 'I am sure we can let you have a house. We have lots of properties.'

A few weeks later, without apparently performing any due diligence, the housing committee approved the allocation of a three-bedroom flat in Holloway to the non-existent protest group. The journalist was told to 'keep it confidential'.

The story appeared in October, the same month that Val Cardwell registered her move to No 1 Cruikshank Street. The property is now worth around £500,000.

Last week, we approached Valerie and Keith Veness at their home. Mrs Veness initially refused to answer questions. But despite her efforts to stop him, her husband was more forthcoming. Mr Veness confirmed that he knew McLaughlin. Indeed, Mr Veness had been, he said, the caretaker of the Islington Council building which became home to the Irish In Islington Project HQ.

He said he was so close to Mr Corbyn that he had ghost- written some of the MP's newspaper articles for him.

Mr Veness claimed Mr Corbyn would not have intervened in securing a flat for Cardwell and McLaughlin. But then he conceded: 'Jeremy . . . might have written a reference. Yeah, he's a fine, upstanding person . . . that's all it would be.'

Then the encounter took an unexpected turn.

While Keith was speaking on the doorstep, his wife could be heard making a phone call inside. When she came back to the door she was suddenly prepared to speak and in detail.

She said: '[McLaughlin's] wife was the tenant. She was in South Wales and she did a council house swap. Somebody [in Islington] wanted to move to South Wales. She came from South Wales because she was attacked. And when he came out of prison, he went to live with her. And they married just afterwards.'

She denied any involvement in the affair, but added: 'I've just checked the facts with somebody who actually knows.' She claimed of Cardwell: 'I knew her by sight. I might have met her once.'

How were Mrs Veness or her unidentified telephone confidant suddenly able to recall such detail about the allocation of someone else's council flat, 36 years after the event?

She would not explain further.

In November 1982, Corbyn had joined the pro-republican Irish In Britain Representation Group (IBRG) which was to back his candidature for Islington.Archives show that, the following month, Corbyn was to chair a meeting at Islington town hall, alongside Val Veness, with guests Gerry Adams and Sinn Fein's PR chief Danny Morrison.

Town hall staff were outraged and the event failed to go ahead only because Adams and Morrison were banned from the mainland after the Droppin Well pub bombing in Ballykelly, which killed 11 soldiers and six civilians.

Then, in spring 1983, a new organisation emerged called the Irish In Islington Project — which was one of a number of pressure groups under the umbrella of Corbyn's IBRG.

Inevitably, the project applied for Islington Council to pay for full-time staff and an HQ. Corbyn sought — successfully — to find funding elsewhere. On August 26, he sent a letter — now in the London Metropolitan Archives — to the Ethnic Minorities Unit at the Greater London Council headed 'Irish in Islington'.

He wrote: 'The work of the Irish In Islington Project is both necessary and desirable, and I urge that their application for two project workers should be met.'

You might already be able to guess who was to be given one of these posts.

McLaughlin was released in the second week of November. His Nantyglo neighbour, Andy Bull, was horrifically injured on November 23. On December 1, McLaughlin took up the post of 'community outreach worker' at the Irish In Islington Project.

The other full-time member of staff was Michael Maguire, a Sinn Fein activist. Maguire later married civil servant Jackie O'Malley, who supplied the Provos with confidential plans to the H-Block prison which enabled the mass breakout of 38 IRA men in September 1983.

McLaughlin had celebrated this in a prison letter, writing: 'What a disaster for the British state . . . it is a measure of the skill and heroism of the IRA that they could do such an escape.'

On December 12, McLaughlin arrived at Islington town hall register office. They gave their residence as 1 Cruikshank Street. Five days later, the IRA bombed Harrods, killing three civilians and three policemen and injuring 90 people. Doctors had just told serviceman Andy Bull that he would never see again.

It would be a horrific Christmas for scores of families. But thanks to Corbyn and friends, Gerard McLaughlin's future was secured.

And as we shall see tomorrow, this wasn't the last of his dealings with Corbyn. Just 13 days after the IRA bombed Mrs Thatcher and her Cabinet in Brighton in October 1984, Corbyn hosted McLaughlin and another convicted terrorist at the Commons.

When confronted by a newspaper, Corbyn at first denied the meeting, but when the story was later confirmed, he said: 'I would be prepared to meet them again in the House, I don't consider there was a security problem.'

Indeed, unashamedly, Corbyn was to maintain close links with McLaughlin until he became Labour leader.

Last night, Corbyn had not responded to our questions about their relationship.

Meanwhile, McLaughlin — who was photographed with Jeremy Corbyn in 2011 — told the Mail: 'I knew Jeremy back in the Eighties and Nineties. He was my MP when I was living in England, but I'm back here now living in Derry so I haven't been in touch with him.'