A contributor to the Scientific American remarked in Animals Underground (April 1898): “There is no doubt that, whatever gave the first impulse to burrow, many animals look upon this to us most unpleasant exertion as a form of actual amusement. It also confers a right of property.”

The pleasure of burrowing is not, of course, confined solely to animals; some humans also possess an irrepressible urge to dig. For instance, the high churchman and antiquary George Henry Law (d.1845), Bishop of Bath and Wells, championed the excavation of the Banwell Bone Caves in Somerset to create what has recently been described as “a solemn reminder of the Flood, a sort of biblical deluge theme park”; and William Lyttle, the “Mole Man of Hackney” (d.2010), felt compelled after having dug a wine cellar beneath his house in a suburban street in east London, to excavate a labyrinthine network of deep tunnels – some as long as 18m in length.

While such extreme compulsions might appear odd, irrational, pitiable and even self-destructive to outside observers, they are, according to Sharon Begley, author of Can’t Just Stop: An Investigation of Compulsions (2017), “responses to otherwise unbearable and even paralyzing anxiety… even the craziest-looking compulsions are adaptive, even pragmatic, and all too human. A compulsion is at once biological balm and curse, surface madness (or at least eccentricity) and profound relief”.

Few people have shown a greater compulsion to dig than the reclusive William John Cavendish-Bentinck-Scott, 5th Duke of Portland (1800–1879). The duke, who was among the richest men in England, was a perverse and enigmatic aristocrat who from the late 1830s lived an isolated life, surrounding himself with “an atmosphere of the closest mystery”.

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