Officers are also searching eight properties linked to the arrested men

Scotland Yard says the arrests are linked to 'Islamist related terrorism'

The home of Yousaf Syed, the 19-year-old suspect, had been raided before

Remaining three men, aged 22, 19, and 25, were held at different addresses

One of the suspects, a 27-year-old, arrested by armed police in the street

Officers will step up security as Queen leads events to mark WWI centenary

Police warned that Parliament and London landmarks could be terror targets

It comes ahead of events honouring the nation's war dead on Sunday

The Queen has vowed to attend the Remembrance Day centenary ceremony at The Cenotaph despite police arresting four Islamist terror suspects plotting to kill her on the day.

The 88-year-old monarch insisted she will carry on with tradition - laying the first wreath following the two-minute silence at 11am on November 11.

A source told the Sun: 'Whatever the security assessment, Her Majesty would not shirk from her responsibility and duty - and this Remembrance Sunday is no different.'

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Terror raids: Four men have been arrested in a series of terror raids, including one here in High Wycombe, Bucks, amid fears

Target: The Queen has vowed to attend the Remembrance Day centenary ceremony at The Cenotaph despite police arresting four Islamist terror suspects plotting to kill her on the day

The Queen's tribute will be followed as normal by salutes from Prime Minister David Cameron, Cabinet members and Opposition leaders.

Yesterday armed officers seized the four men, aged 19 to 27, following months of surveillance.

Last night police were said to be interrogating the suspects - who are thought to have hatched a plot assassinate the Queen with a knife.

Police had already stepped up security after a terrorist shot a soldier guarding a war memorial at Canada’s parliament.

A police officer guards this property in Desborough Avenue, where a neighbour said officers were searching a shed. The timing of the raids raised fears of a Remembrance Day outrage

A ring of steel will be thrown around Whitehall today as the Queen leads events at the Cenotaph marking the centenary of the start of the First World War.

Although police would not discuss whether the suspects had a specific target, the timing of the raids raised fears of a Remembrance Day outrage.

Islamic State militants have called on ‘self-starter’ followers to target high-profile commemorative events.

Police marksmen from its SO15 terrorism command arrested the youngest suspect on Thursday night at 8.31pm at the £160,000 home he shares with his mother in High Wycombe, Buckinghamshire. He is said to have recently returned from Pakistan.

Fourteen minutes later a 22-year-old was seized by armed officers at a house in Hounslow.

A ring of steel will be thrown around Whitehall tomorrow as the Queen leads events at the Cenotaph to mark the centenary of the start of the First World War

In an unusual move, the eldest suspect was stopped at gunpoint in his car in Southall, West London, but no shots were fired.

The fourth man was arrested in Uxbridge and searches were taking place in Greenford and Hayes, also in West London.

The suspects were all arrested on suspicion of being concerned in the commission, preparation or instigation of acts of terrorism.

It was reported the allegations are linked to a UK plot - not travelling to Syria to join ISIS.

The use of armed officers for the arrests suggests police chiefs fear the suspects may have acquired weapons. None were found, however.

The Metropolitan Police said the operation involved its counter-terrorism command, MI5 agents and officers from other constabularies.

The home of Yousaf Syed, the 19-year-old suspect, had been raided before – in April during an investigation into potential jihadists.

Another man arrested in that operation complained his passport was seized by the Home Office to stop him travelling to the Middle East.

Neighbours of Syed said he lives with his 41-year-old mother Somia, who works as ground crew for an airline.

One said he had had ‘several run-ins’ with the ‘angry’ teenager.

When he challenged the teenager’s mother, she told him: ‘I’m sorry, it’s my son. He’s young and he’s just discovered his faith.’

The neighbour said the teenager recently grew a full beard and began wearing traditional Muslim dress.

Another local resident said: 'It's a big shock to hear what he's been accused of.'

Officers were said to have removed items from the garden shed as forensic officers combed the house and garden.

Today two police officers wearing high visibility jackets were posted outside the brown wooden front door of the brick terraced house in Desborough Avenue, near the town centre.

A cordon of police tape was placed around the brick driveway to the home, on which a police patrol car was also parked.

All the curtains were closed at the terraced house where police forensic staff were combing the home and garden for clues while neighbours stood in the street and watched.

The neighbour said that he saw a woman, the teenager, a man aged in his 20s along with two small children regularly coming and going from the address.

He said that he had been out when the raid took place early this morning and that he arrived back at his home to find officers removing items from the family's shed.

Two other addresses in the town were being searched, including a rented flat and a £300,000 house apparently occupied by Syed’s aunt.

High Wycombe’s remembrance parade is due to take place at 10.30am tomorrow in the high street before proceeding to All Saints’ Church.

It attracts large crowds, in part due to the proximity of the town to RAF High Wycombe in nearby Naphill.

A large contingent of personnel from the base, which is the home of the RAF’s Headquarters Air Command, traditionally marches with veterans and other community groups.

Investigation: These officers were guarding the front door of this High Wycombe house while forensics worked inside

Germaine Lindsay, who killed 26 people when he detonated a bomb on the Piccadilly Line in the 7/7 attacks, has links to High Wycombe.

There are growing concerns that British jihadists fighting in Syria and Iraq will return to this country and carry out acts of terrorism.

But detectives do not believe there is any direct link between the latest arrests and fanatics in the Middle East. David Cameron ordered a security review last month after the Canadian attack.

Heads of MI5 and Scotland Yard held talks over the terror threat to Parliament and other landmarks in central London.

Just a few weeks ago police were warned to be on their guard over fears they could become targets.

Raids: Scotland Yard said that they have arrested four young men in a series of raids linked to an alleged Islamist terror plot

In London, frontline officers were warned of intelligence that suggested terrorists aspired to abduct and murder a policeman. In August the national terror-threat level was raised from substantial to severe, meaning a terrorist attack was ‘highly likely’.

A Metropolitan Police spokesman said the men were being held on suspicion of ‘being concerned in the commission, preparation or instigation of acts of terrorism’.

He said the arrests were part of an ongoing investigation by the Met’s counter terrorism command, colleagues from other forces and MI5.

He added: ‘They have all been taken to police stations in central London and remain in custody. Two of the entries to premises were assisted by firearms officers. No shots were fired.’

On Remembrance Sunday in 1987, 11 people were killed and 68 wounded when the IRA bombed the cenotaph in Enniskillen, Northern Ireland.