Nick Timothy, a former adviser to the home secretary, said: "We already knew that Sadiq Khan spent years campaigning to prevent the extradition of Babar Ahmad, who pleaded guilty to terrorism offences in the US. Now he appears to have links with an organisation that was connected to Anwar al-Awlaki, and became part of the notorious Cage. London faces a serious threat from terrorism: anybody who wants to be its mayor should show better judgment."