The man behind a “sinister” plot to blackmail Asda stores across the Black Country out of thousands of pounds has been jailed.

John Botwood, from Bilston, threatened to inject oranges with acid and to hide needles and shards of glass inside food items. The 50-year-old, of Lees Terrace, was jailed yesterday after he admitted two counts of blackmail committed between 2000 and 2008.

He claimed that he had never wanted to make money, it was instead an “intellectual experiment into the criminal mind”.

Birmingham Crown Court heard that he had cost the supermarket tens of thousands of pounds in security bills and up to 50 officers from West Midlands Police’s serious organised crime unit had been working to catch him.

He had evaded capture for almost a decade but was finally brought to justice when he was arrested on a separate charge of assault in May 2009 and his DNA matched a sample taken from one of his letters.

Jailing him for two and a half years, Recorder Anthony Warner told him: “Your threats were sinister and you have engendered alarm in the staff at Asda.

“The company took your threats of contamination very seriously, not just at the branches concerned, but nationwide.”

Botwood, a former security guard at Birmingham’s City Hospital, had £69,000 worth of debts when he made his second blackmail attempt in 2008, the court heard.

But he never carried out any of his threats and never received any money.

He started the unsuccessful plot in 2000 when he sent six threatening letters to the manager of the Tipton branch of Asda in Wednesbury Oak Road, demanding that £2,000 be paid to him using a credit card.

In 2008 he targeted the stores on the Queslett Road in Great Barr, and at the One Stop Shopping Centre at Perry Barr in Birmingham, sending nine letters.

He demanded that £15,000 be paid onto a ‘Prime’ credit card.

In his defence the court was told he was not motivated by becoming rich, but by trying to find out if such an offence could be carried out.