National Crime Squad officers raided the farm in July 2002

But four other people were cleared by a jury at Lewes Crown Court of illegally producing amphetamines.

The court heard the owner of the farm had been producing the drugs for more than three years before being caught last summer.

He was jailed for 12 years, while a dealer who sold the drugs was given a 10-year sentence.

'Delia Smith recipe'

The court heard farm owner Kevin Hoare, 46, had produced up to six tons of 'speed', worth an estimated �20m, at his home, Bugsell Mill Oast in Hurst Green.

The jury was told he manufactured the drug using a process as simple as "a Delia Smith recipe".

He would pass the drugs on to 42-year-old Graham Pierce, of Greyswood Street, Streatham, London, to sell on, the court heard.

The operation only came to an end when National Crime Squad officers raided the premises last July.

Among most serious offences

Hoare's sons, girlfriend and a handyman were enlisted to help produce the drugs, but the jury decided they had no idea it was amphetamines they were making.

They cleared Adam Hoare, 20, Russell Hoare, also 20, and Alan Smith, 50, all of Bugsell Mill Oast, and Tracey Thaker, 35, of Vicarage Way, Hurst Green, of producing a class B controlled drug.

Kevin Hoare was convicted of producing and supplying a controlled class B drug and Pierce found guilty of supplying the drug.

Sentencing Hoare to 12 years in jail and Pierce to 10 years, judge Guy Anthony said their crimes were among the most serious types of offence imaginable involving amphetamines.