As the waters rose, the protests became louder. Once more, the UK’s flood defences had been found wanting. The prime minister’s operationally-unnecessary but politically-vital urgent visit to flooded areas caused further questions as to the country’s anti-flooding strategy, tactics and funding.

The news media are working around the clock to bring us minute-by-minute updates on what is happening where. Rolling TV and radio news, and newspaper websites bring the reader right into the heart of the affected areas. Printed newspapers are at a disadvantage; they need something different and lo and behold some of them have dusted off their perennial campaigns to raid the overseas aid budget. Sadly, this evening, Facebook is looking like a bit of a cesspit. The nonsensical cliche ‘Charity begins at home!’ is the intellectual high point of the debate, after which it deteriorates quickly. The essential point is that some people don’t like this country’s commitment to the world’s poorest people. Today they’d like that money to be spent on flood relief. Tomorrow it will be the NHS, or veterans, or education. As Michael Sheen is supposed to have said on Radio 4, that’s what the 99.3% of UK-based spending is for.

I don’t profess to knowing how much money we should be spending on flood defences. How much would we save from not building on flood plains? What of reforesting the uplands and mountain areas (wooded areas trap extreme rainfall very effectively)?

But what I do know is that it is the government’s first job to defend its citizens – from enemy agents but also, where possible, from treatable environmental calamity. And the armed forces have been called in to support communities (and the emergency services). This is a matter of the defence of the realm.

You would never place the Ministry of Defence under the control of someone who didn’t believe in the necessity, from time to time, of using the armed forces. Yet the last Environment Secretary, Owen Paterson, was widely regarded as a climate change denier who seriously weakened the country’s ability to deal with the phenomenon.

Sandbags aren’t as exciting as counter-terrorism gadgets. But the government needs to take this type of security seriously. The money should come from the defence budget. (The defence budget should be raised accordingly – but it isn’t as though the Chancellor can’t find money for what he regards as priorities.) Let’s reiterate: the government’s first job is to defend its citizens. And it’s increasingly clear that defence begins at home.