It’s much easier to dismiss an absurd claim that is fresh and new than one which has been around for a while and taken root. It is, for example, simple enough to assess the credibility of David Icke’s assertion that Dr Josef Mengele – seemingly after he died – used mind-control to make a young American woman go to Balmoral Castle and officiate at rituals where the Queen and Queen Mother turned into reptiles and devoured small children; or to judge whether, as ‘Sir’ Laurence Gardner tells us in an explanation on which his whole ‘grail bloodline’ theory depends, the otherwise unmentioned daughter of Joseph of Arimathea (in this version, the brother of Jesus Christ) popped over to Wales to marry and settle down with Bran the Blessed, a mythical god-figure who spent much of his life as a detached head (and who, even if we take the original myths as a guide, would have been well over 100 years old at the time of the marriage).

Dislodging established and much-repeated nonsense is much more difficult, but that doesn’t mean we shouldn’t try.