British PM facing flak Still in charge: Prime Minister David Cameron, on holiday with his wife, Samantha. British Prime Minister David Cameron visited MI5 headquarters to thank spies for their around-the-clock work in the aftermath of the Woolwich terror case despite concerns there had been failings by the security services. Details of his visit to MI5's headquarters emerged on Sunday as Mr Cameron flew to Ibiza over the weekend on a family holiday, leading to questions about his judgment over the case. Downing Street said he "remains in charge" of Britain as he was pictured in a cafe with his wife, Samantha. A spokesman said he has taken staff with him so he can be kept informed about the investigation into the murder of Drummer Lee Rigby. Both of the men accused of killing him had been monitored by the security services for years but were not deemed a threat to life. Kenyan authorities recently said they had warned British security services about one of the men and his links to extremism, but claim they were ignored. Mr Cameron's visit to MI5 to praise spies before these details were made public, coupled with his decision to go on holiday, has been criticised in the aftermath of the worst terrorist atrocity on British soil since 2007. The family of Drummer Rigby visited the scene of his murder in Woolwich, where his mother and sister were so overwhelmed they collapsed on the roadside. Home Secretary Theresa May said the attack was not the work of a "lone wolf," as four other men were arrested at the weekend in connection with the murder. Extremist preachers could be barred from appearing on broadcasters such as the BBC under government plans to expand the powers of Ofcom, the watchdog. Lord Howard, the former Conservative home secretary, suggested Labour and the Tories join forces to push through a "snoopers' charter" against the wishes of the Liberal Democrats. The day after Drummer Rigby was murdered Mr Cameron announced the Intelligence and Security Committee would investigate what the intelligence services knew about the alleged killers. After visiting the scene of the Woolwich attack, Mr Cameron paid a trip to security services headquarters. He thanked staff for their work on the investigation and counter-terrorism. However, a Westminster source suggested it was a mistake to praise spies so soon after the tragedy and amid concerns of potential intelligence failings. The security committee will receive a report on Wednesday into the death and then consider the terms of a future probe. Michael Adebolajo, 28, had been known to the security services and police for a decade and was arrested six years after protests by extremists outside the Old Bailey. In November 2010 he was arrested in Kenya after being caught trying to travel to Somalia, allegedly to join the terrorist network al-Shabaab. Kenyan authorities say they returned him to British intelligence officers, who failed to take their concerns seriously and tried to recruit him as a source, reports suggested. The second suspected killer, Michael Adebowale, 22, was also known to police and intelligence services.