John Stonehouse is put into a more senior Goverment position. In 1966, Labour win a
far larger majority, and are able to hold into Goverment through 1970. During this period, it is publicly revealed that Stonehouse has been working for the
Czech Secret Service, sparking a whirlwind of accusations of spying. Healy is burned for his former membership to the Communist Party, and several other Hard Left Ministers and Secretary of States (Tony Benn and Eric Heffer spring to mind) have their careers ended by accusations. Eventually this reaches Wilson, who is openly 'outed' as a Spy for the Soviet Union, and interrogated by MI5. The Tories and Liberals use this as a stick to beat Labour, with violence breaking out in the streets between the right and left.
With Enoch Powell or a fellow far-righter likely to be Leader of the opposition, there would be some hard times ahead for the British Left.