Hertfordshire

The Grove in Hertfordshire is considered the most likely venue.

Steve Ryan, a food technology teacher from Hertfordshire, told the BBC there was "much less respect for teachers than there ever used to be" and that staff were leaving schools "in droves".

His decision to sell off the Covent Garden offices and move production to a business park in Borehamwood in Hertfordshire was met with protest.

Matthew Keating, of High Street, Rickmansworth, Hertfordshire, was sentenced to seven years and six months in prison for conspiracy to import Class B drugs.

Hertfordshire Police said the arrests "were necessary to fully investigate the allegations" but there was "insufficient evidence" to take any action.