A State level cover-up of very very serious crimes linked to British intelligence services could not be carried out or successful unless the Head of the Department was in on the 'game-plan' to play their respective roles in the cover-up of the crimes, if not they would have caught the culprits and put them on trial which is what they are employed to do.
It would not be successful unless the Chief was 'in on it', it then goes down the line with whoever is involved in the network.
Why would they want to cover-up very serious crimes using the Power of the State when they are employed to counter such serious State to State crimes on our behalf?
Obviously because they are not working in the best interests of the British State, unless Cameron agrees with the cover-up and with MI5/MI6 being complicit in mass murder in Norway and planned mass murder in Sweden along with a failed mass murder attempt on British streets they are linked too, which in my opinion must mean they are working in the interests of a foreign Power.
Namely Russia in my opinion based upon my knowledge.
Work the rest out yourself.