International Marxist Group
The International Marxist Group (IMG) was a Trotskyist group in Britain between 1968 and 1982. It was the British Section of the Fourth International. It had around 1,000 members and supporters in the late 1970s.  In 1980, it had 682 members; by 1982, when it changed its name to the Socialist League, membership had fallen to 534.  At that point all its members had joined the Labour Party.