Four men and a woman were today being quizzed by police after one of the UK's biggest amphetamine factories was found at an isolated Sussex farm.

The National Crime Squad says the plant was capable of producing 20kg of the drug with a street value of £1m every week.

Detective Chief Inspector Jim Warnock said: "This is a major find and we believe we have disrupted a major drugs conspiracy."

A woman in her 30s was arrested at a farm in Hurst Green, near Robertsbridge, and two men were arrested simultaneously in Streatham, south London. Another two men were arrested in Hurst Green late last night, police revealed today.

Experts from the Forensic Science Service, who are helping examine the building, described it as one of the most sophisticated and productive plants they had seen.

The three people arrested were being interviewed by National Crime Squad officers at police stations in south London and Sussex.