On 12 May, 1976, Professor Yuri Orlov, a Soviet physicist, founded a Group to Promote the Observance of the Helsinki Agreements in the USSR. This was the first of many such similar groups in Eastern Europe and had nine members to begin with. On the day of its foundation, Professor Orlov was warned by representatives of the KGB that his action was unconstitutional and illegal, but no evidence was offered to support this accusation. In the course of the following year the Group issued 19 major reports on violations of the Helsinki Accord in the Soviet Union, and on 10 February, 1977, Professor Orlov was arrested on unspecified charges. In May 1977, Professor Orlov's wife retained the English barrister, Mr John Macdonald, to act as her husband's defence lawyer, but Macdonald was refused a visa to enter the Soviet Union. He then hit upon the idea of conducting his case for the defence of Orlov in the form of a special tribunal, at which evidence was heard from several dozen expert witnesses, including some former members of the Helsinki Group now in the West. The tribunal was held at the Institute of Physics in Belgrave Square, London, on Monday 13 June, and the evidence subsequently transcribed and submitted to the Soviet courts for consideration. What follows here is a condensed selection of some of the testimony that was offered.