An undercover police officer posing for years as an environmental activist co-wrote a libellous leaflet that was highly critical of McDonald's, and which led to the longest civil trial in English history, costing the fast-food chain millions of pounds in fees. Lambert was deployed by the special demonstration squad (SDS) – a top-secret Metropolitan police unit that targeted political activists between 1968 until 2008, when it was disbanded. He co-wrote the defamatory six-page leaflet in 1986 – and his role in its production has been the subject of an internal Scotland Yard investigation for several months. At no stage during the civil legal proceedings brought by McDonald's in the 1990s was it disclosed that a police infiltrator helped author the leaflet.