The BBC's Phil Mackie: "Keys claimed money grew in the boot of his car"

Martin Keys, 32, a shift manager at the warehouse in Bicester, was found guilty of stealing £500,000 worth of chocolate - weighing more than 300 tons - by a jury at Gloucester Crown Court on Thursday.

He will be sentenced on Friday.

Keys attempted to explain away the large quantities of cash that had suddenly appeared in his bank account as the result of a bizarre investment scheme.

He claimed that he simply left cash in the boot of his car and contacts who he could not name took it away and returned with ever larger quantities of money.

Attracted attention

Prosecuting counsel Simon Brand dismissed his alibi as "preposterous story which no-one could possibly accept".

There was "a whole mass of circumstantial evidence", he said, to prove that Keys was the "brains" behind the Mars bar scam.

During an 11-day trial, the jury heard how eight lorry loads of chocolate worth approximately £70,000 each were driven away from the Tibbett and Britten warehouse in Bicester.

Keys, from Stow-on-the-Wold, Gloucestershire, then used his knowledge of the computer system at the warehouse to cover up the thefts.

He attracted attention to himself when he started banking large sums of money and bought a Saab convertible car for £21,000 cash.

'Worldly wise'

He also paid £52,000 in cash towards a new house where he went to live with his girlfriend Emma Smiley, 25, shortly after he left his wife Helen.

Ms Smiley was cleared of money laundering charges, despite the allegation that a person "of even average intelligence" would have questioned how Keys had afforded his lavish lifestyle.

Her defence counsel Terry Munyard said she had accepted that her boyfriend was "worldly wise" and had made some money before he met her.

Mr Munyard said Keys had "wooed" Ms Smiley with presents, expensive meals, flowers and - of course - chocolates.