Boston bombing prompts security increase at Margaret Thatcher's funeral

MI5 are concerned that Republican splinter groups are plotting an attack on Britain

Police officers on the look out as Thatcher's body arrives at the Crypt Chapel of St Mary Undercoft in the Houses of Parliament (Getty Images)

Police and the security services are monitoring dissident Irish Republicans as part of a huge security operation for today’s funeral of Baroness Thatcher.

The activities of extremists from Northern Ireland are being tracked ahead of this morning’s procession through central London – which will be targeted by left-wing protesters – and a service at St Paul’s Cathedral attended by 2,000 mourners, including the Queen and foreign dignitaries.

The move came as it was announced that security would be increased in response to the terrorist attack on the Boston marathon.

Sir Bernard Hogan Howe, the Commissioner of the Metropolitan Police, said there would be an increase in manpower and searches during the event as counter-terrorism officers seek to establish whether the bombings in America have any potential link with Sunday’s London marathon.

This morning, teams of police arrived on The Strand at 7am and had closed the road to traffic by 8am. Officers will be placed at intervals of 10 metres along the whole route, with more at crossings. Others patrolled the road on motorbike and horseback, with more on the pavements on foot.

The first spectators arrived at Downing Street at 6.30am but by 9 o'clock Parliament Square still remained relatively quiet.

It is understood there have not been any major changes to the policing arrangements for today’s ceremony and this weekend’s race but senior officers have contacted their American counterparts for information about any threat to Britain. Sir Bernard said: “We are reviewing our plans, which is sensible... What we are doing is to take reasonable steps. We will increase searching and we are making sure there are extra staff. But we have no reason to believe that people are any less safe than they were yesterday.”

The review of the security plan came as police prepared to deal with demonstrations expected along the route of the ceremonial procession conveying the former prime minister’s body from Westminster to St Paul’s. Shopkeepers and businesses along the route have been asked to remove any “loose tools” or ladders which could used by demonstrators to gain access to buildings. A branch of HSBC bank near St Paul’s will also briefly close before the funeral.

An officially sanctioned “turn your back” protest planned near the Royal Courts of Justice could be attended by more than 400 people who have pledged to participate on Facebook.

MI5 and counter-terrorism police have been concerned for several years that Republican splinter groups are actively plotting an attack on the British mainland. Officials believe the funeral of Lady Thatcher, who remains a hate figure in some nationalist circles, may present an opportunistic target either in Ulster or the mainland.

Police in Northern Ireland have said they will bring in resources to deal with expected protests in Londonderry. About 25 petrol bombs were thrown in clashes last week in the city’ and a protest is expected in the area today.

Commander Christine Jones, the Yard officer in the charge of the joint operation which will see 4,000 officers on duty in central London, said police were seeking to balance their duty to protect public safety with the right to stage peaceful protest.