So Michael Gambon stitches up his best mate Bill Nighy by expecting him to expose the PM, after Gambon's character snuffs it.
Placing Nighy's career and life at major risk.
If Gambon thought he was about to kick the bucket, why not just leave it for the papers in the event of his death? Why involve Nighy?
Spoilers!
My take is this was a very subtle way for Gambon's character to get back at Nighy's for leaving his wife when she was pregnant, especially since Gambon then married her and raised Nighy's daughter. It was obvious there was a lot of strain happening between the former marriage partners and Nighy's relationship with the daughter.
They were still good mates but his loyalty to his wife came first.
I don't share that viewpoint, Gambon's relationship with Nighy's was very strong indeed.
Rather, I think Benedict saw the information as a way of safeguarding the future of the service. He needed Worricker to use the information as he himself would have, if his health had permitted. Which is exactly what Worricker did. Simply releasing the information to the press may have brought down the government, but it would not have preserved the service.