Just as News International threw Andy Coulson to the wolves in advance of last week’s PMQs, so at yesterday’s the PM did the same.

In truth however, if Mr Cameron’s former communications director ‘turns out to have lied to me’ of course it will say something about Mr Coulson. But it will also say something about Mr Cameron and his judgement and character.

When Tony Blair asked me to work for him, I sat down and I went through things in my life that were likely to be trawled over, and which might embarrass him. A drink problem. A breakdown. Violence. A patchy record at university to say the least. I told him who my enemies were and who my friends were, so that he could make a judgement on that too. He made his own inquiries by talking to others. He pressed me a bit, and after it all said ‘I am not bothered if you’re not bothered’. In other words he made a judgement based on as full an assessment as he could make.

If there are any researchers with nothing much to do today I would love to count the number of times I have written about the Cameron-Coulson relationship and asked on this blog if Mr Cameron had the eyeball to eyeball conversation that would allow his judgement to be applied.

He took Mr Coulson’s word for it. Fine. He took Mr Murdoch’s word. Mmm, ok. But he was being warned privately and publicly by many wiser and more independent counsel that it was a mistake. He chose only to hear what he wanted to hear.

There are also questions – which the government seem reluctant to answer – about the vetting process Mr Coulson went through after Mr Cameron took him to Downing Street.

Yesterday I bumped into Paddy Ashdown, one of the people who warned Cameron privately whilst many others were doing so publicly. He said if Cameron’s judgement was so poor in this, it would call it into question more insistently from now on in.

Mr Cameron did what he had to yesterday, but he is being dragged by events not leading them. George Osborne’s role in this is also questionable, though he is doing a good job at keeping his head down. He it is who wanted Coulson in there. He too therefore must face the charge that his desire to get someone he thought would be the best clouded his judgement. He parades as a great strategist. But this was a tactical error with profound strategic implications.

So now the dam has burst on Murdoch and Mr Cameron hopes his new indignation and the judicial inquiry will halt the dam bursting on him.

I caught the end of Newsnight and well done to the Tory MP Louise Mensch for making clear her side too wanted to see the inquiry go beyond News, in her case (as in mine) to the Mail in particular for the corrosive impact its standards and practices have on our national life (not to mention its starring role in the Information Commissioner’s previous investigations).

A word about my old paper the Mirror too. Today columnist Brian Reade has a pop, saying I was the one who got TB to cosy up to Murdoch and so who am I to talk now? And he suggests the media rounds I have doing have been to promote my new book.

First, try telling that to the publishers. I have refused to do the round of bookplugging interviews despite many many requests.

I have done the interviews I have done on the current situation, and said what I have said here, because I have experience of both sides of the fence and I think this is an important moment for the media-politics relationship; a subject on which as Brian knows I have had strong views for a long time.

It is partly the journalist in me, as well as the political voice, that hopes we can now move to a position where politicians do their job without fear or favour, and journalists do their job without fear or favour. It will be healthier all round, and better for the public. But I would say from the press reaction so far that the politicians get this better than the journalists.

One final point on the Mirror. I have been trying to find out why my old paper hired Jonathan Rees, and paid him well, for inquiries in relation to me half during our first term. I have asked Piers Morgan, who no longer seems willing to comment on all this. Mr Reade’s article reminds me I should keep on asking.

In any event, I assume Mr Justice Leveson will want to know why newspapers pay large sums to private detectives. Could it be that they do the things the journalists cannot do within the law?

So for Cameron, questions of judgement. For all politicians, questions about why we tolerated this situation for too long. For the police, questions about their competence and in some cases their integrity. And for some of our journalists, questions about culture and practices that will now be far more far-reaching than they would have been had they listened earlier to some of the criticisms that have come their way.

I repeat my comparison with the trade unions pre-Thatcher. They did not see what was coming because they saw only what they wanted to. A bit like Cameron too.