I went along to the Worthing Dome at the weekend to see the film Darkest Hour, and it was extremely good – atmospheric, brilliantly acted and it reduced some of the audience around me to tears. Gary Oldman’s performance is really extraordinary.

But since the credits rolled, I have been trying to analyse why it worried me, and I have two reasons I came up with.

First, it isn’t as accurate as it could be. The atmosphere felt right, and the broad thrust was correct, but there were too many details that irritated. The generals and admirals were portrayed as deer caught in the headlights. The idea of asking the little ships to Dunkirk was re-imagined as a last minute idea by Churchill himself, foisted on an unkempt Admiral Ramsay. In fact, the original appeal had been broadcast on 14 May, four days after Churchill took office and two weeks before they were used.

The idea that most soldiers were taken off by small boats is absolute nonsense – the vast majority were taken off by destroyers and cross-Channel ferries (you can find out more about what really happened in my short book Dunkirk).

The conversation at Churchill’s ‘outer cabinet’ completely missed the point. Not for the first time, I wondered why scriptwriters can’t just tell the truth, as it is known. The truth is quite dramatic enough.

My second nervousness is exactly why we are being given these dramas of those weeks, where the nation hung in the balance, and why now. It has to be that film-makers, even American ones, sense some parallel between this Brexit and the last one, when – within a few days (and for good reasons) – we dropped out of our remaining European alliances and had to furiously rethink policy on absolutely everything, and at breakneck speed.

So I’m nervous about the critique of Lord Halifax’s diplomacy – not because he was right (he wasn’t) – but as if there is now a real choice between Halifax’s negotiation and Churchill’s will to fight. As if we are being invited to support Churchill’s romanticism against the exhausted realism of everyone around him.

And somehow the infuriating peddling of the little ships myth, in this film and Dunkirk, seems to sum up the problem. History doesn’t repeat itself like this.

I have been wondering whether it is the weaving of unhelpful mythology that yesterday led Theresa May to give a cautious welcome to an idea that would have been regarded as anathema to previous generations of British policy-makers – that we should have a two-year transition from EU membership, legally obliged to pay into the budget and accept any rule changes they set, without any say on these and other matters at all.

Where is Churchill now? He was after all, not just a great Briton, but a great and far-sighted European. He was also a realist. Otherwise we would never had survived.

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