In another episode, Thornton is sent to Saigon, against the backdrop of the Vietnam war. Alec Stewart is arrested in Algiers as a spy and imprisoned – although eventually released, he receives little trust or support from his colleagues. Brian Stead, returning to Berlin for the first time since 1945 to oversee a natural gas drilling deal, finds his past coming back to haunt him in a nasty plot to discredit him by a rival company. The Mogul organisation was reputed to have been based on BP and there were many similarities and coincidences in terms of the international events "The Troubleshooters" predicted. "The Troubleshooters" lasted for seven series from 1965 to 1972, making the transition from black-and-white to colour along the way. In the final episodes, Brian Stead maintains control of Mogul and fends off hostile enemies, but at the cost of his own health. Stead eventually steps down as company director, but not before finally naming his successor. Today the legacy of "The Troubleshooters" lies in its bridging the gap between "quality drama" and populist entertainment and charting a linear path trod by later British television serials, such as "The Brothers" and "Howards' Way". The series struck a chord with the 1960s audience thanks to its format - a potent combination of the oil business, globe trotting power politics, corporate wheeler-dealing and sex. It had parallels with the contemporaneous ATV board-room drama "The Plane Makers" (later renamed "The Power Game"). The series was subject to the BBC's wiping policy of the era, but some episodes still remain in the BBC archive, including the series opener "Kelly's Eye". Only one colour episode survives as broadcast ("Camelot on a Clear Day", a copy of which can be viewed at the National Media Museum in Bradford, UK); all other existing colour episodes only survive in the form of black-and-white film recordings. A previously missing episode from series two - "Birdstrike" - was returned to the BBC by a private collector in May 2010, with the assistance of classic TV organisation Kaleidoscope. The five surviving episodes of series one were released on DVD in the UK by Danann Publishing Ltd. in 2016.