In the late autumn of 1985, the investigative journalist Duncan Campbell was commissioned by BBC Scotland to make several documentaries for its "Secret Society" series. One of them featured a new UK sigint satellite codenamed Zircon. Zircon was then perhaps Britain's most secret defence project. It was also controversial because, like a previous defence project called "Chevaline", its costs had been hidden from the the Parliament's Public Accounts Committee, raising constitutional issues. In late 1986, the BBC Governors became increasingly concerned about the sensitivity of the programme and sought government advice. The authorities insisted that the programme be halted on security grounds and the BBC complied. The Observer broke the story on 17 January 1987 with the headline "BBC Gag on £500m Defence secret".
Duncan Campbell revealed more details of the matter in the New Statesman magazine in an attempt to evade an injunction by Treasury Sollicitors. Robin Cook MP attempted to show the programme in the House of Commons, but this was prevented by the Speaker of the House, Bernard Weatherill. Police Special Branch raided the offices of BBC Scotland and Duncan Campbell's home over the weekend of 24-25 January 1987. The BBC Controller for Scotland, Pat Chalmers, was questioned for several hours by police and papers and film footage were confiscated.
The affair represented the high watermark of tension between the BBC Governors, led by Marmeduke Hussey, and the Director-General, Alastair Milne. The Board of Governors asked for, and obtained, Milne's resignation on 29 January 1987. The programme was finally show on television in 1988.