Holly Willoughby remains under police guard after a plan to kidnap and harm the star was uncovered

UK TV host Holly Willoughby is under police guard at her London home after a plan to kidnap and "seriously harm" the star was uncovered. 

The This Morning host was alerted of the plan by police just shortly before she was due on-air, and ultimately decided to pull out of the show.

Willoughby was replaced with Alison Hammond who joined her co-host Josie Gibbon.

READ MORE: David confronts Victoria for lying in new docu-series

Hammond and Gibbon skirted around the topic, with fans quick to notice there was no reason given as to why Willoughby was absent. 

However an Essex Police spokesman has now revealed: "A 36-year-old man from Harlow has been arrested on suspicion of conspiracy to kidnap as part of an ongoing investigation.

"The arrest was made on Wednesday 4 October.

"He is currently in custody."

It's unclear exactly how police became aware of the man's plans, though it seems that his mobile phone and other digital devices were seized, containing 'sinister messages' threatening to "seriously harm" Willoughby. 

One neighbour of the man said: "I saw him being led out of his flat in handcuffs last night at about nine o'clock."

While another added that a forensic van had been parked outside earlier, and a police car is now posted outside his flat.

The suspect is in police custody and is not personally known to Willoughby. 

READ MORE: A brief history of the 'naked' dress

A source revealed: "Investigations are continuing but police are treating this as a credible conspiracy to kidnap Holly.

"There were apparently some sinister and threatening messages found on electronic devices threatening to seriously harm her."

A round-the-clock police presence has been posted at Willoughby's home where she lives with her husband and three children.