The Scottish documentary film-maker Brian Barr, who has died aged 70 from cancer, was one of those journalists for whom integrity was more important than self-promotion or material reward. In 1986, Brian helped reveal one of Britain's greatest postwar security scandals, when he and the investigative journalist Duncan Campbell exposed the existence of a £500m spy satellite which the government had somehow omitted to mention to parliament – Project Zircon. Working on a tipoff, they confirmed the existence of the project by putting a surprise question, during a filmed interview, to a visibly shocked government scientist, Professor Sir Ronald Mason.
Afterwards, special branch officers raided the Glasgow headquarters of BBC Scotland in the middle of the night and seized all film related to the programme, which had been made for the Secret Society series. This ignited one of the most explosive confrontations between the Thatcher government and the BBC, and played a major role in the resignation of the director general, Alasdair Milne, in 1987. The government took out an injunction preventing transmission of the film, but after a number of unauthorised screenings by anti-censorship campaigners it was eventually shown by the BBC in 1988. Brian always loved to quote the Paisley Daily Express headline "Ex-Paisley choirboy in spy scandal".
Brian was born in Paisley to Anna Cattanach and James Barr. His father was musical director of the Glasgow Corporation and Brian took up the oboe at Paisley grammar school. This and his love of swimming perhaps accounted for his extraordinary lung capacity. On arduous excursions in the Scottish mountains, he would intimidate everyone by putting in a five-mile run before breakfast.
Brian was, as he put it, "somewhat over-educated", having degrees in law and philosophy from Glasgow University. But he never seriously thought of becoming a lawyer, and his interest in philosophy was, he once told me, ignited by a desire to get better acquainted with the woman who was to become his first wife, Jean. They married in 1968 and had a son, Colin, who also became a documentary maker.
The intellectual discipline Brian acquired at university was put to good use. He had an extraordinary ability to assimilate a vast quantity of information and render it intelligible. His career began in that incubator of Scottish journalists, the Sunday Post of DC Thomson in Dundee. He progressed to the role of leader writer at the Glasgow Herald in the early 1970s before leaving to edit a community newspaper, the Glasgow News, which he sold around the city's bars and restaurants at weekends.
In 1975, he joined BBC Scotland as a reporter on the weekly documentary series Current Account. His films explored issues such as asbestosis in Clyde shipyards and lead in Glasgow's water supply. His coverage of the workers' occupation of the Scottish Daily Express, and its brief rebirth as the Scottish Daily News, won widespread acclaim and led to a book, The Story of the Scottish Daily News, co-written with Ron McKay and published in 1976.
Brian was not politically partisan, but his approach to authority was uncompromising and this inevitably clashed with the safety-first culture of BBC Scotland. Other films in the Secret Society series produced by Brian included The Secret Constitution, about cabinet committees; We're All Data Now, about data banks; In Time of Crisis, about government emergency powers; and A Gap in Our Defences, about botched radar contracts.
Brian's contribution to broadcast journalism was greater than his actual film credits, though these are substantial enough. He made fine films from many of the world's conflict zones for BBC programmes such as Panorama and Assignment, and for Channel 4.
He seemed to have a magnetic attraction for the police. I recall going on assignment with him into the seedy underworld of Glasgow's sex industry and arriving with cameras at an illegal club at the moment it was about to be raided by Strathclyde police. This was pure coincidence – but the police believed otherwise. In the 1990s, when filming for the Channel 4 series Secret Places at RAF Chicksands in Bedfordshire, Brian was apprehended by armed US soldiers and then detained by Biggleswade police for 12 hours. He was arrested by the Israel Defence Forces, incarcerated by police in Algeria and nearly shot for trying to attach a microphone to Yasser Arafat in Palestine.
Brian was completely fearless, whether scrabbling up rock faces in the Scottish highlands or filming in war zones. His greatest professional weakness was an inability to deal with bureaucrats and line managers. Like many Scottish film-makers, he found it increasingly difficult to get commissions in his later years. However, he never stopped working – co-writing a book on the river Spey with his brother Donald and making community films in the Isle of Bute where he mostly lived. Almost all those who worked with him through his long career felt they learned from him and were inspired by his example.
Brian is survived by his second wife, Pat, whom he married three days before he died, and by his son, Colin, from his marriage to Jean, which ended in divorce in 1999.
• Brian Barr, documentary film-maker, born 21 November 1942; died 29 October 2013
