It is supposedly November 1941 yet the opening sequence of the BBC's new series, SS-GB, has a Spitfire Mk IX flying over London and landing on the Mall. A "resistance fighter" shoots the German pilot, is captured and taken away in a Bedford QL Army truck.
As it turns right in front of a bombed-out Buckingham Palace, one can make out two tanks in the forecourt of the Palace. One looks to be an M-40 Patton and the other could be a Sherman.
Yet, the Spitfire Mk IX did not enter production until June 1942. The US-built Sherman did not enter production until February 1942 and the M-60 is a post-war US tank, entering production in 1959. As to the QL, volume production did start in March 1941, but it is unlikely that, in a nation defeated in the Battle of Britain, it would have entered production at all.
Even at this late day, there are still vehicles and aircraft which were built on or before 1940, which could have been put to good use. But such is the BBC's dedication to accuracy that anything vaguely from that period is good enough. Any old rubbish will do for mere license payers.
For Booker though – taking a break from Brexit – there are other issues. "Dear BBC", he writes in his column, "there are better 'What Ifs' than SS-GB".
The newspapers, he says, naturally found it as irresistible to publish pictures of swastikas draped in front of a ruined Buckingham Palace as did the BBC to concoct its "What if? " mini-series, SS-GB, on what life in Britain might have been like if the Nazis had successfully invaded in 1940.
Such speculations about how different the world might look if only some historical event had gone another way have long been popular, not least back in 1930.
It was then that an American magazine commissioned well-known writers of the day to produce essays (later published in a book, If: History Rewritten) on what a different course history might have taken if, for instance, the Dutch had held on to what became New York, or Napoleon had escaped to America, instead of being captured after Waterloo.
The best-known of these contributors was Winston Churchill, ever eager in those days to earn a hefty fee for dashing off a piece of journalism. "Perhaps it might amuse an idle hour", he wrote, "at this moment in the 20th century, so rich in assurance and prosperity, so calm and buoyant", to meditate on what might have happened if General Lee had won the battle of Gettysburg and the South had won the American Civil War.
It is certainly entertaining, Booker suggests, to see Churchill describing the world in 1930 as "prosperous, calm and buoyant", just as America was plunging into the Great Depression and only three years before the rise to power of Hitler.
But years ago, he tells us, he recalls noting, when he first read of Churchill's essay, that "all 'What if? ' questions about history are posed by the devil". In other words, rather than speculating about things which didn't happen, it is far more interesting to peel away the myths and false "narratives" which constantly befog history and try to uncover what really did happen.
This is particularly relevant to the long-standing myth of Hitler's supposed plan to invade Britain in 1940. It is true that many at the time imagined this might be imminent. Booker's father, who was a special constable in 1940, used to recall how a favourite topic of speculation in Honiton police station was how many of the town's councillors, if the Germans did invade, would have been ready to collaborate. The general conclusion was "all but one".
But the really interesting truth, he avers, referring to my "admirable book" on the Battle of Britain, The Many, Not the Few, was that Hitler never had any intention of invading Britain. His purpose all along, as he told his High Command in July 1940, when the aerial battle was approaching its height, was simply to cow Britain into suing for peace, thus allowing him to concentrate on his real agenda, an invasion of Russia.
His prime purpose that summer was to use his bombers, first to destroy Britain's economic lifelines, air force and military production, and then, by blitzing London, to demoralise the British people into no longer wishing to resist.
That handful of supposed invasion barges in ports across the Channel were just part of the show. Hitler's generals were fully aware that they simply didn't have the resources to mount an invasion of Britain.
Meanwhile, no fewer than five times between July and October, he put out peace feelers, in the hope the British would bow out of the war on generous terms, even being allowed to retain much of their empire.
Fortunately the prime minister was not Halifax but Churchill. So the Blitz continued relentlessly until, on 10 May 1941, it suddenly stopped – because Hitler had sent his bomber fleets east to prepare for the invasion of Russia weeks later.
Of the many myths still surrounding the Battle of Britain which my book dispels, this one deserves to be as firmly buried as any. And to explain this would have made a much more grown-up use of the BBC's airtime than that miserable little bit of self-indulgent play-acting that its baffled viewers have been straining their ears to follow.
The trouble is, of course, that the "Battle of Britain" has now become a multi-million pound industry, all part of the larger "nostalgia" industry that sustains thousands of jobs in pursuing a version of history which has become absorbed into our national identity.
Never mind that the image of the Cockney slum-dweller, emerging from the wreckage of his bombed-out home, a cheerful grin on his face, and a defiant quip about Hitler on his lips, was pure invention, devised by Fleet Street editors at one of the weekly lunches with the "Minister for Information".
Never mind that the only newspaper that ever got close to telling the truth about what was happening on the ground, The Daily Worker, was closed down by the Government, and critics about the inadequacies of British policy and equipment were silenced.
That much is necessary and probably justified in war, but there is no excuse for historians to embellish the propaganda and to offer it as the literal truth, for want of finding out what really went on.
The great shame is that the truth is actually so much more interesting than the incoherent pap that we have on offer, and so much better than this lame, fictional version of something that did not and could never have happened – one where they can't even be bothered to get the basic props right.
In years to come, I suppose, we will be seeing the same treatment dished out on the EU Referendum, when all the great and good line up to describe their roles in winning the battle. And the truth then will be as far away from what we are told as what we are currently told of the Battle of Britain.