Nice dig in his resignation speech at Cameron
"Once Mr Wallis's name did become associated with Operation Weeting, I did not want to compromise the Prime Minister in any way by revealing or discussing a potential suspect who clearly had a close relationship with Mr Coulson. I am aware of the many political exchanges in relation to Mr Coulson's previous employment - I believe it would have been extraordinarily clumsy of me to have exposed the Prime Minister, or by association the Home Secretary, to any accusation, however unfair, as a consequence of them being in possession of operational information in this regard. Similarly, the Mayor. Because of the individuals involved, their positions and relationships, these were I believe unique circumstances."