The tough task facing Brown's children

As Sir John Chilcott's Inquiry into the war in Iraq continued to chip away at Tony Blair's historical reputation this week, another of the former Prime Minister's closest allies took his leave of frontline politics.

Amid difficulties in his private life that will surely elicit widespread sympathy, Alan Johnson became the latest in a long line of key players from the Blair Years to depart the political stage.

Looked at in terms of Labour kremlinology, the erstwhile Shadow Chancellor's surprise resignation, and his replacement by Ed Balls, means the Brownite takeover of the party is now all but complete.

Mr Balls, Ed Miliband, Yvette Cooper and Douglas Alexander were all denied Cabinet promotion by Mr Blair – but they now occupy the four most senior roles on the Labour frontbench.

But in this lies the nub of Labour's problem as it seeks to come to terms with opposition and put itself back into credible contention for government.

For as time goes on, it is becoming clearer and clearer that the general election result last May was not just a repudiation of Gordon Brown personally, but of much of what he stood for politically.

There are increasing signs that, like 1979, 2010 could come to be seen as a watershed election, a moment in history which saw a paradigm shift away from the top-down, statist brand of politics with which Mr Brown was associated.

That is certainly the way the Coalition would like us to see it, which is why the proposed reforms to the National Health Service announced this week are so central to its overall political strategy.

The reforms are certainly not without risk for Prime Minister David Cameron. With the possible exception of Coronation Street, the NHS remains Britain's best-loved institution and politicians tinker with it at their peril.

Not the least of Mr Cameron's difficulties, as Alastair Campbell pointed out on Question Time on Thursday night, is that he has no electoral mandate for it.

But the voters tend to be rather less worried about private vs public arguments in public service provision than politicians - and political commentators for that matter – tend to be.

And as long as the service improves in time for the next election – as it may well do once the dust has settled – it could even turn into a vote-winner.

The risk for Labour, on this and other issues, is that it finds itself stranded on the wrong side of a political tide – much as it did in the early 1980s as Margaret Thatcher's free-market revolution forged ahead.

Of all the blows that the Coalition has landed on Mr Miliband since he became Labour leader, none was more telling than Mr Cameron's "I'd rather be a child of Thatcher than a son of Brown."

In truth, Ed Miliband was really only ever an adopted son. The true son of Gordon, the one who was by his side in all his most important decisions, was Mr Balls.

Sure, the combative new Shadow Chancellor will give as good as he gets, but it is already clear that the Coalition will exploit his closeness to the former Prime Minister to the limit.

On the surface, Balls for Johnson looks like a good exchange for Labour – a brilliant economist and pugnacious operator for a Mr Nice Guy who seemed out of his depth in the Treasury brief.

But the whole reason Mr Johnson was appointed to the role in the first place was precisely because he had no economic baggage.

The Coalition's key success since the election has been to pin the blame for the cuts on Labour's mismanagement of the economy and to fix this in the public's mind.

Mr Balls, of all people, is going to have his work cut out to reverse that perception.