Sadiq Khan, the London Mayor, has never been briefed on the Hizbollah bomb factory plot uncovered on the outskirts of the city in 2015, despite being in office for more than two years.

The Daily Telegraph understands that Mr Khan was not made aware of the discovery despite the Metropolitan Police, which he oversees, playing a central role in disrupting the activity.

Boris Johnson, who was Mayor of London when the plot was uncovered in the autumn of 2015, was also not informed according to his deputy mayor for crime and policing at the time.

Stephen Greenhalgh, who was in post when the plot was uncovered, told The Daily Telegraph that he and Mr Johnson tended to be briefed together by the Met on counter-terrorism matters.

The revelations put pressure on UK government ministers and Metropolitan Police leaders to explain why the public, MPs and even politicians overseeing the Met were kept in the dark.

This newspaper revealed how figures linked to Hizbollah had been caught storing three tonnes of ammonium nitrate – a common ingredient in homemade bombs – in North West London.

Four properties were raided by the Met on Sept 30, 2015, and a man in his forties was arrested on suspicion of terrorism offences, though he was released without charge.