Why has concrete suddenly become headline news?

We must admit, we'd never heard of reinforced autoclaved aerated concrete (RAAC) until the other day.

But deep within certain and very particular corners of government, it has been a talking point for years.

So why has this suddenly become headline news?

Let's examine the anatomy of this particular issue.

Over the summer, a school ceiling collapsed. Until then, it hadn't been flagged as critical.

This, alongside other incidents and assessments from Department for Education (DfE) officials, led Education Secretary Gillian Keegan to conclude the government had underestimated the potential dangers of RAAC.

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Conversations took place around a week ago between Downing Street and the education department and it was agreed action was necessary.

Ministers were braced for difficult questions but felt they had no alternative.

It has led some at Westminster and beyond to wonder if Ms Keegan has overreacted.

Her allies say the facts had changed and she has been "more proactive on RAAC than any other government minister in the world".

Enter next, Jonathan Slater, the former permanent secretary at the education department - its most senior civil servant. He was sacked three years ago.

Mr Slater claimed in a BBC interview that there was a "critical risk to life" if the school repairs programme was not funded.

He said up to 400 schools a year needed work, but the department got funding for 100 while he was the senior official, which was "frustrating".

He was optimistic this would rise to 200 after he left. The actual number was 50.

As far as we can work out, the promise to fund 100 was never made public.

The government's spending review three years ago committed to "rebuilding 500 schools in England over the next decade".

The spending review two years ago said the same, working out at 50 a year.

The prime minister claimed Mr Slater's attack on his record was "completely and utterly wrong".

Let's unpick this a little.

We have been speaking to people who were involved in those private negotiations within government.

What do they recall of what happened then?

One figure acknowledged there was "an accepted need to address the issue of RAAC".

But, they added, there was little sense that it would be imminently dangerous.

The big picture context at the time was one of the country and the government recovering from the pandemic.

The context in the DfE was a focus on free schools and the need to boost funding per pupil.

The issue of replacing RAAC in schools featured in the discussions between the education department and the Treasury, we are told - but only briefly.

And, one well-placed source told us, it is unlikely the issue would have ever reached Rishi Sunak.

In short, the DfE was concerned about RAAC, but had other pressing political concerns at the time too.

And the Treasury wasn't persuaded it was pressing, and hadn't been for some time.

Rightly or wrongly, the government then had one position on the risk of RAAC and its relative importance.

And, rightly or wrongly, the government now has a rather different one.

Critics of the Conservatives suggest spending cuts over the last decade or so of their time in office are responsible.

What is also worth considering is the insight this crumbling concrete offers into ministers' choices, judgements and attitudes to risk, both now and in recent years.

Some of this is related to money. But instincts, priorities and context are key too, in the DfE and beyond - then and now.

It is how these have shifted - in the light of what has happened this summer - that has led to the consequences we are seeing, and will continue to see.