Mark Bayliss, 20, Russell Robinson, 18, and Laura Mason, 22, will appear before Stevenage Magistrates charged with "being concerned together in blackmailing Judith Baker", a spokeswoman for Hertfordshire Police said.

Bayliss, of no fixed address, but formerly of Vallance Drive, Cheshunt, Herts, and Robinson and Mason, both of The Avenue, Bengeo, Hertford, were charged after a major investigation into the alleged kidnap of a policeman's son.

The investigation, which was a combined effort by Hertfordshire Police and the National Crime Squad, began on Tuesday, when police secured a media blackout.

A fourth man, aged 18 and from Hertfordshire, has also been arrested in connection with the inquiry.