They came, as they always come, in the dead of night. As a middle-class family slept at their home inside a high-security compound in an affluent part of Kigali, the capital of the African republic of Rwanda, they were about to awake to a nightmare.

For, as crickets chirped in the hot, still air, the country’s dreaded secret police, bristling with weapons, were silently scaling the walls using ladders.

After dropping into the compound, they burst into the house and rammed guns in the faces of the terrified occupants — a young American-educated woman accountant, her sister and mother. The goons shackled all three and drove off with them into the night.

For days, friends and family were baffled by the women’s disappearance, and feared criminals had kidnapped them. The truth was more sinister: state-controlled media announced a week later they were being held at an undisclosed location on charges of high treason. ‘During ongoing investigations, police uncovered credible evidence linking the trio to offences against state security,’ police said in a chilling statement. ‘There is evidence to suggest they were plotting to overthrow the government.’

To his opponents Paul Kagame is a butcher and a war criminal who runs a brutal one-party state. Paranoid and convinced that coup plotters are everywhere, he regularly purges loyalists in the army

The woman they arrested is Diane Rwigara, daughter of a wealthy Rwandan businessman, who was educated in Belgium before achieving a masters at San Francisco State University and taking up a teaching post at the Ivy League Stanford University.

Diane returned home to Rwanda last year, but any prospects of a glittering future are now gone. She had been harassed for months, with police calling at her door in the middle of the night and her phones tapped, before she ‘disappeared’ at the end of last September.

Diane’s house has been seized by the government and is being put up for auction. A commercial property, a factory and flats she owned have been knocked down. Her life savings of £250,000 were stolen by the police who arrested her. Fake nude photographs of her were posted on the internet.

This week, as I drove past where one of Diane’s properties once stood, my Rwandan companion whispered that the bulldozers moved in to send a message: ‘The president is saying: we will crush you, and the grass will grow and no one will remember you were ever alive.’

Her crime? She tried to stand against Rwanda’s president Paul Kagame in elections, calling for an end to his reign of murder, looting and tyranny. That was a mistake for which she is paying dearly. This week, Diane is spending her 268th night behind bars in the hellish Mageragere Prison, a place so terrifying that my driver would only take me within half a mile for fear we would be spotted and thrown inside.

The man who put her there is a stick-thin teetotaller and erstwhile close friend of former British Prime Minister Tony Blair, who calls him a ‘visionary’.

Cherie Blair, meanwhile, in her professional capacity as a barrister, was instructed to defend Kagame’s feared spy chief, who is wanted for questioning about the murder of a British aid worker.

At one time, Kagame gave Blair the use of his Bombardier private jet to travel around Africa.

Yet to his opponents Kagame is a butcher and a war criminal who runs a brutal one-party state. Paranoid and convinced that coup plotters are everywhere, he regularly purges loyalists in the army.

Now, the world will be hearing more of this dictator following the announcement that Arsenal, one of the world’s most famous football clubs, has struck a deal to market his country on their shirts with global television audiences of hundreds of millions.

In return for the cash, Arsenal’s players will bear the legend ‘Visit Rwanda’ against a pink backdrop on one sleeve of their iconic red-and-white shirts. Kagame hopes TV viewers will flock to his country.

Such is the tyrant’s interest in football that he was to be found this week in Moscow attending the World Cup, where he was warmly greeted by Vladimir Putin.

Diane Rwigara is unlikely to be celebrating the news of the Arsenal sponsorship. Mageragere Prison sits on an isolated peak deep in the remote countryside. Here, Rwanda’s Alcatraz is surrounded by watch towers with armed guards and a forbidding wall with razor wire and electric fences. Nobody has ever escaped.

He was credited with ending the genocide that saw almost one million people die during a 100-day orgy of violence against his own Tutsi tribe and moderate Hutus by rival Hutu extremists. But according to a UN report, after the civil war he sent his men on a psychopathic pogrom against the Hutus (pictured: bones excavated from a mass grave after the genocide)

Inside is a place of horror. The prison was relocated here from the centre of Kigali because screams from prisoners and the stink of excrement were embarrassing the president, who has spent millions on public relations experts to burnish his image.

The location may be new — but the brutality remains the same. Beatings, mock executions and widespread sexual abuse of female inmates are a way of life. In a searing report, Human Rights Watch investigators uncovered evidence last year of the scale of the abuse, which includes guards forcing inmates to fight each other for their enjoyment.

Kagame — referred to in Rwanda as the ‘darling dictator’ due to attempts by the rich and powerful to curry his favour — tells anyone who will listen that he has transformed his country since his forces invaded in 1994 from neighbouring Uganda.

He was credited with ending the genocide that saw almost one million people die during a 100-day orgy of violence against his own Tutsi tribe and moderate Hutus by rival Hutu extremists.

Kagame was fawned over by Western politicians. But according to a UN report, after the civil war he sent his men on a psychopathic pogrom against the Hutus. (Kagame’s government dismissed the UN report as ‘outrageous’.)

Hidden from prying eyes, Rwandan forces are accused of hunting down Hutus, chasing two million into neighbouring countries, killing tens of thousands and triggering a humanitarian crisis.

While other infamous African dictators such as Uganda’s Idi Amin and Mobutu Sese Seko, of Zaire (now the Democratic Republic of the Congo), were lunatics, Kagame is a more clever and devious despot.

‘The centre point to his policy is convincing everyone that he is a good guy who provides street lights and is doing his utmost to transform Rwanda,’ one Western diplomat told me. ‘But the reality is he is doing his utmost to transform his own finances and cling to power at all costs.’

As well as vast wealth derived from the mineral riches to be found in neighbouring countries, Kagame also controls almost every aspect of business life in Rwanda.

So why on earth has Rwanda been given almost £1 billion of UK taxpayers’ money via foreign aid over the past decade?

The funding was part of David Cameron’s plan to detoxify the Tory Party. Yet, as long ago as 2010, warnings were sounded about Kagame’s barbaric regime.

At a meeting in Whitehall to plan Cameron’s first trip to Africa after becoming Prime Minister, he was urged not to visit Rwanda or meet Kagame because of the human rights abuses. Cameron decided to go anyway, thinking it would look good if he was seen to be helping a small African country devastated and torn apart by the genocide.

The aid gravy train for Kagame ran into problems in 2012 when Rwandan-backed rebels wreaked havoc in the neighbouring Congo, raping and murdering, with reports of mothers being forced to kill their own babies by pounding them into pieces in large bowls used for grinding corn into flour.

Britain suspended its aid programme briefly in 2012 — then reinstated it. Today, Kagame is still active in Congo, plundering minerals and funding militias, while for all the donor cash pouring into Rwanda, more than half the population live on less than £1 a day, and famine is widespread.

Despite that, Kagame’s regime has now found the money to spend £25 million on sponsoring Arsenal.

One man less than enamoured to hear about the deal is Will Turnbull, who lives just a few miles from Arsenal’s Emirates Stadium. His brother Graham, a UN worker, was in Rwanda probing atrocities by Kagame when he was murdered by the new Arsenal sponsor’s regime. The man named as Graham’s killer was Karenzi Karake, Kagame’s spy chief.

Pictured: Diane Rwigara, who was arrested for trying to stand against Kagame in elections, and calling for an end to his reign of murder, looting and tyranny

Yet after Karake was arrested during a trip to London and accused of the killing of civilians, Cherie Blair was hired to represent him and used legal arguments to prevent him being extradited to Spain to face other charges over the deaths of three Spanish aid workers.

‘The multi-million-pound deal with Arsenal is nothing short of a self-indulgent vanity project,’ Will Turnbull told me. ‘Yet again Kagame is short-changing his people for his own ends. It is shameful he is allowed to act unopposed both at home and abroad.

‘Is it not time the UK and other European nations stood up against this desperate regime and offered assistance to Rwanda’s people?’

For their part, in a statement to the Mail, Arsenal said: ‘Rwanda has transformed itself dramatically in recent times and is now regarded as one of the most advanced and respected countries in Africa. This is one of the reasons we believe that, having conducted due diligence, it is a partnership that will help Rwanda meet their tourism goals while developing football in the country.

‘Tourism is one of Rwanda’s fastest-growing and biggest industries. It has helped dramatically reduce the country’s reliance on foreign aid, whilst significantly contributing to the GDP and employment of Rwanda, and this partnership is intended to accelerate these benefits.

‘The partnership is with The Rwanda Development Board and focused on driving awareness of what Rwanda has to offer as a tourist destination to millions of people around the world.’

Of the 1.4 million tourists Kagame claims visit the country every year, Rwanda admits that only 92,000 people were from the U.S. and Europe. The larger figure includes those returning from neighbouring African nations.

In fairness to Arsenal, carrying out ‘due diligence’ is tricky, as I discovered. The regime regularly jails journalists, and few foreign reporters are allowed in, apart from travel writers invited to extol the natural beauty of the country and its population of rare mountain gorillas.

Investigative journalists do not prosper here: hit squads have killed two of the country’s best reporters, shooting them in the head at separate locations and dumping their bodies by the road.

There is no free Press. The internet and social media are monitored. Websites are regularly blocked. In 2012, the BBC was banned after airing a documentary challenging Kagame’s version of life in Rwanda.

A vast flow of aid has certainly transformed the capital, which is marketing itself as the ‘convention centre’ of Africa, with expensive hotels bustling with diplomats and officials from governments and charities around the world.

Yet the majority of ordinary Rwandans face a daily nightmare just to survive. The scale of woe was evident this week when I visited Kimisagara, an overcrowded slum on the outskirts of the capital where life is wretched, with disease and poverty rife.

There seemed little evidence of any aid money being spent to ease their plight. A doctor at one crumbling clinic, where locals have to pay 50p per visit (almost half of the average daily income), told me that typhoid, malaria and chronic diarrhoea were commonplace.

When asked what the cash given to Arsenal by his government could do for the poor and ill, this medic smiled apologetically and said carefully: ‘It’s the president’s choice how he wants to spend the money. I hope it’s a good thing. We trust our president.’

Now, the world will be hearing more of this dictator following the announcement that Arsenal, one of the world’s most famous football clubs, has struck a deal to market his country on their shirts with global television audiences of hundreds of millions (pictured with former Arsenal player Tony Adams)

At a bar nearby, a group of men playing pool on a torn, rickety table — all ardent football fans — laughed bitterly at the largesse given by Rwanda to a rich, world-famous football club.

‘It’s the president — what can we say,’ one told me, smiling weakly. ‘We don’t have anything here — no work, no money, no nothing. We don’t have lives.’

Kagame has spies everywhere. Each village has an agent working for the regime, who must report daily with details of every aspect of life among the locals — from mundane matters such as gossip about affairs, to listening in for any plots against a man his loyalists call Number One.

Nor are critics safe abroad. Kagame’s directorate of military intelligence has been blamed for a number of killings of defectors overseas, including the strangling of a former spy chief in a South African hotel room.

Paul Charles, a former BBC newsreader, acts for Kagame from his offices in London’s Notting Hill. In a series of emails to me, he denied the regime has wasted millions on public relations to burnish its image. ‘First, president Kagame is not personally sponsoring his favourite football club,’ he stated.

‘The contract with Arsenal is with the Rwanda Development Board, which is responsible for promoting and marketing tourism and business investment into Rwanda.

‘Its marketing budget for the Arsenal partnership is totally separate to foreign aid received, which is spent on local projects with approval of the UK Government.’

Mr Charles refused to comment on the plight of Diane Rwigara, saying that it was a matter for the Rwandan government. We asked the Rwandan authorities a series of questions about abuses uncovered during my investigation, but they also declined to comment.

Back in one of Kigali’s slums — where mud-built houses have been marked with crosses for demolition so high-rise apartments can be built for the ruling elite — a man named Michael was convinced that Arsenal would soon be seen playing at Kigali International Stadium.

‘Even if I have to pay back the money for all my life, I’m going to get a ticket and see them,’ he beamed.

I didn’t have the heart to tell him that Arsenal will not be coming. The club told me: ‘No, the players won’t come. Rwanda gets the exposure through our shirt, space on matchday advertising boards and players will be involved in tourism campaigns.’

As I walked the streets of Kigali, along pavements built with aid money, I pondered whether perhaps Arsenal’s stars should wear two armbands: ‘Visit Rwanda’ in pink on one sleeve, and on the other a photo of the imprisoned Diane Rwigara, to commemorate all those kidnapped, tortured and murdered by their rich new sponsor’s appalling regime.