Closing Ranks

I saw this one on the Washington, DC PBS station back in 1982, I think, I recall being pleasantly surprised. A Soviet KGB agent defects in London with tales of treason within British intelligence. The stories seem believable, but is the defector for real, or only a plant, designed to sow havoc and unrest within an Allied intelligence service? Remarkably precient, given the "defection" to the West just three years later of a man said to be a high-ranking Soviet intelligence official who subsequently redefected to Moscow. I hope someone gets the idea to bring this one out on VHS or DVD.