Holly Willoughby: Gavin Plumb guilty in kidnap and murder plot

In a statement, Ms Willoughby said: "I will forever be grateful to the undercover police officer who understood the imminent threat, and to the Metropolitan and Essex police forces for their swift response."

The defendant, who had previous convictions for attempted kidnap, wept in the dock as he was told he would be sentenced on 12 July.

Det Ch Insp Greg Wood, of Essex Police, told the BBC that Plumb was an "obsessive loner" who had assembled "all the items he needed to cause Holly Willoughby some serious harm".

"If the American officer hadn't have contacted us… I've got no doubt that Gavin Plumb could've gone on to commit some really horrific crimes," he added.