Is there a Hitler in our midst? This week's most improbable claim was that Unity Mitford secretly gave birth to Adolf Hitler's lovechild before giving the poor little mite up for adoption. The evidence is anecdotal and has not impressed serious historians. But this has not stopped speculation that this supposed product of Anglo-German fellowship is alive and well and shopping in Surbiton.

As it happens, for many years some of Hitler's closest relations were living in Britain. Keen to make a name in the safety-razor trade, his half-brother, Alois, moved to Liverpool. He set up home with Brigid, his Irish wife, in Toxteth. It was there, in 1911, that their son, William Patrick Hitler, was born. Sadly, Alois, who apparently had a bit of a temper, deserted his family. Returning to Germany, he married bigamously and while his sibling was ordering Europe around, Alois was running a tearoom in Berlin.

Between 1930 and 1939, home for Brigid and her son Pat was 26 Priory Gardens, Highgate. Those who knew “the Hitlers at No 26” spoke well of them. Even as Europe's skies darkened in 1938, the Führer's sister-in-law was cheerfully assuring The Daily Express: “Nowadays it's a bit embarrassing to be Mrs Hitler, but the people who know me don't mind, and the others don't matter.”

As late as 1972, The Times could confirm: “The Hitlers were good and friendly neighbours, according to people who still remember them in Highgate.” By then though, they had long since departed North London. Mrs H pre-empted a court summons for non-payment of rent set for the day that her brother-in-law invaded Poland by emigrating to New York. From there, she helped out with the British War Relief Society.

Pat Hitler also arrived in the United States, denounced “My Uncle Adolf” and served in the US Navy. But he had previously hoped to cash in on the Führer's fame in Germany rather than notoriety abroad. Moving to the Reich in 1933 and becoming a car salesman, he repeatedly approached his uncle hoping for preferment. When he was rebuffed and told to renounce his British nationality, he threatened to allege to the press that the family had Jewish antecedents. Soon persuaded that this would be unwise, he packed his bags and departed Germany.

After the war, the Hitlers settled in Long Island and opted for anonymity under an assumed name. Brigid died in 1969 and Pat in 1987, leaving behind his German-born wife and three children, Alex, Louis and Brian. None of these sons became fathers.

Only two mysteries remain. What possessed Pat Hitler to have his son Alex christened in 1949 with the middle name Adolf? And, given the Führer's admiration for the racial theorist, Houston Stewart Chamberlain, was it not unfortunate that the family adopted as its new surname Stuart-Houston?

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