This is a Foreign and Commonwealth Office travel advisory for British nationals thinking of visiting Iran. Political and cultural obstacles to carefree adventure holidays do still exist here, but the grave risks long associated with the legendary quicksands of Daryacheh-ye Namak salt lake, near Qom, do not. In fact, they never did. For science has proven that quicksand, of itself, cannot be fatal. It may be able to devour an entire screaming damsel on Golden Age celluloid, but in real life, according to a paper in Nature whose author began his research at Qom, it always stops sucking once its victims are chest-deep. The proof is based on the physics of fragile sand matrices, which collapse into dense silt once disturbed, and on Archimedes’ principle: in essence, what floats naturally in water must do so in quicksand.

Thus, this advisory must be taken to refer to all unstable and generally exotic-looking swaths of sand so long as they are not vulnerable to tidal waters; and, retrospectively, to at least 34 motion pictures of varying renown including Supergirl, Leech Woman, Lure of the Swamp and The Hound of the Baskervilles. We regret to say they all turn out to be pure fantasy.

The same may even be true of Arnold Schwarzenegger’s exploding head in Total Recall (do not, therefore, venture to Mars without a suitably stout helmet) and Krook’s death by spontaneous combustion in Bleak House, even though Dickens insisted to his own end that it was based on fact. Science is not yet able to declare the Bermuda Triangle safe for seafaring Britons, though we fear Dr Simon Spoilsport may be about to in his new book, Why Real Life Doesn’t Suck.