Four men have been arrested in connection with an alleged Islamist terror plot before tomorrow's Remembrance Sunday commemoration.

Counter-terror police detained the men, aged 19 to 27, overnight at locations across west London and High Wycombe, Buckinghamshire.

It is understood the arrests followed a planned attack on British soil by people inspired by Islamists. One report suggested a knife attack was to have taken place at the Queen's visit to a Royal British Legion event today at London's Royal Albert Hall.

One of those being held is said to have returned from a trip to Pakistan earlier this year.

Police vehicles and tape could be seen outside two addresses in High Wycombe, where one of the men, a 19-year-old, was arrested, as officers carried out searches of the properties.

There were a series of arrests late on Thursday and early yesterday in towns across west London which involved armed officers.

Police held a 22-year-old, a 19-year-old, a 25-year-old and a 27-year-old, who was stopped in a car.