Too Secret Too Long
Chapman Pincher
'Was
 there a Soviet mole in the highest reaches of the British secret 
service? British journalist Chapman Pincher thinks so, and he thinks it 
was Roger Hollis, who was head of MI-5 from 1956 to 1965. Pincher takes 
some 600 pages to weave his web of circumstantial evidence, and in doing
 so takes us once again through all the now familiar but still 
engrossing cases of British spy-traitors-Burgess, Maclean, Philby, 
Blunt, George Blake, Gordon Lonsdale (the list is very long). The 
evidence is indeed suggestive, but Sir Roger has been dead since 1973. 
One wonders if there is much more to mine in this vein. But still the 
drilling goes on.' (Foreign Affairs website review)