Quote: "The point raised was Blair/Campbell manipulation of the press and the BBC - there are plenty of examples of New Labour approach to message manipulation'"
I agree that this was when the era of 'spin' started in earnest and it was a change for the worse.
There had always been some form of press management: Bernard Ingham pushing tabloids to present stories in the form of "Maggie Acts" in the 1980s, but the difference was Thatcher wasn't basing her decisions on the headlines. Even Blair wasn't, he was just trying to swing public opinion his way, through media management. But he went against public opinion on tuition fees and Iraq.
The David Kelly / WMD stuff was a significant shift in terms of degrading public opinion in government and that is on Blair.
The Cameron era was when it really started going downhill in terms of a) making decisions based on the press story (a classic hallmark of an Osborne budget), b) moving from spin being the job of political appointments/Spads to expecting civil servants to be "on message" with "defensive lines" and demanding that impact assessments got signed off by Ministers (with anything the Minister didn't like, susceptible to being taken out).
Johnson has taken this to the nth degree, with actively misleading the public and taking an ambivalent attitude to scrutiny. Even May felt the obligation to try and explain herself to Parliament and the public. Johnson has the approach of entitlement, I'm the PM, I can do what I want lol.