pasir
In the Burgess and Maclain affair British intelligence would repeat such incompetence when in later years they were warned by Canadian Intelligence that a British University trained traitor had infiltrated the highly secret Atomic research establishment - but again chose to ignore the tip off.
"but again chose to ignore the tip off" - a little disingenuous I think.
Presumably you are referring to the atom spy Alan Nunn May who was exposed by the defection of Igor Gouzenko in Ottawa in September 1945.
Igor Gouzenko was a GRU (Soviet Military Intelligence) cipher clerk in the Soviet Embassy in Ottawa who defected to the West in September 1945. Gouzenko passed copies of GRU documents implicating British scientist Alan Nunn May. The British were advised of this.
Nunn May was questioned at Harwell on 15th February 1946 (the day after it became public knowledge that Gouzenko had defected), questioning continued and on 20th February 1946 he confessed he’d been in touch with a Soviet agent, and had given the agent a report on atomic research and two samples of uranium.
On 1st May 1946 Nunn May was tried at the Old Bailey and after a one-day trial, sentenced to ten years hard labour.
Alan Nunn May’s treachery and investigation is mentioned extensively in Christopher Andrew’s authorized history of MI5 “The Defence of the Realm”.
The National Archives list the relevant MI5 files available for public scrutiny here:
Atom spy Alan Nunn May and related files | The National Archives
As regards the "Englandspiel" Christopher Andrew mentions this on The National Archives web site:
In 1942, the operation by the British Special Operations Executive, SOE, to land Dutch agents in occupied Netherlands, was penetrated by German agents, which used the agents' codes to lure SOE into sending more agents and to provide them with intelligence and supplies, both of them quickly snaffled by the Germans.
In all, about 50 Dutch agents were identified, captured and executed, and among the new MI5 releases is the file of Adolf F-, a German agent who took part in the Englandspiel, and was interrogated about it by MI5 after the Second World War, and there are also files of a series of other real or suspected German agents and German intelligence officers in the new releases
See here:
MI5 file release August 2010 | The National Archives