Police have foiled seven terror attacks since the Westminster atrocity in March, Sadiq Khan has revealed.
The London Mayor said counter-terror experts have told him there has been a shift in the threat, rather than a spike in attacks, this year.
There have been five attacks in Britain this year but police have thwarted more over the same period of time.
Mr Khan told a Guardian live fringe event at Labour's party conference in Brighton: "The phrase used by police experts, counter-terror experts, in relation to terrorism is what we're seeing is not a spike but a shift.
"And the reason why they say that is because if you look at the time when Fusilier Lee Rigby was murdered in 2013 up until the Westminster Bridge attack this year, there were 13 terrorist attacks thwarted because of the excellent work of the police and security services.
"If you look at the time between March of this year and now, yes there have been four terrorist attacks (in London) but there have been seven that have been thwarted."