Fellow PPruners should take with a grain of salt anything written by either Chapman Pincher or Peter Wright. Both were fantacists who did the public and political image of the intelligence community grave harm.
That book by Leigh about "The Wilson Plot" does a pretty good job of outing Peter Wright as the uncontrollable lying conniving conspiracy schemer he really was. By implication Leigh also destroys much of Pincher's work as well - as Wright was one of Pincher's major sources
I suspect Leigh probably also has inaccuracies - but its interesting to read as a counterbalance to the raving hysteria of "Spycatcher", and Pincher's related offerings.