Ferris was arrested in London in 1997 following a two-year surveillance operation by MI5 and Special Branch. At his trial at the Old Bailey in July 1998 he was sentenced to ten years imprisonment after being convicted of conspiracy to sell or transfer prohibited weapons, conspiracy to deal in firearms and possessing explosives, although the sentence was reduced to seven years at the Court of Appeal in London in May 1999. While in prison Ferris co-authored his biography "The Ferris Conspiracy" with Reg McKay, which sold 20,000 copies while he was imprisoned. Ferris was released from Frankland Prison, County Durham in January 2002 pledging to give up his life of crime, and released a second book with McKay, a novel titled "Deadly Divisions", in April 2002. In May of the same year he was sent back to prison for breaching the conditions of his parole after being involved in a knife fight with Tam McGraw, and an alleged connection with a £900,000 shipment of cannabis (later proven to be fictionalised by newspapers and police). Official reports say he was wounded in the knife fight, but witnesses say he was free of recent wounds. As to the cannabis shipment, the other accused had not been in contact with Ferris for many years. Ferris was released again in June 2002, and returned to Scotland.