Victorians understood the need for social distancing. Young ladies, as we know, had to be chaperoned in public, and we might imagine the mid-century crinoline added a measurable seclusion zone. But a much more insidious evil emerged in the nineteenth century, one which threatened the very foundations of British society: indecent--as in naked--male bathing at the seaside.

Men and boys had always stripped off to swim in secluded rivers and lakes, so when sea-bathing took off in the eighteenth century, via segregated beaches, there was seemingly little concern about their doing so in the nude. Plunging head-first into the sea was recommended by doctors in medical tracts from the 1750s. There were different views on the best time of day to bathe and what diet you should follow. Some physicians recommended a fortifying glass of wine before a swim; several warned of the dangers of eating fruit. Few medical texts, however, had anything to say about bathing apparel.

Wealthy Georgians took to the seaside for the same reason they frequented spa towns: for that agreeable combination of health-cure and fashionable society. Then, between 1793 and 1815 when Britain was at war with France, came travel restrictions. The appeal of accessible British seaside resorts grew. Jane Austen's Mr Parker says that one of the main attractions of the fictional seaside town Sanditon is its most desirable distance from London: "One, complete measured mile nearer than Eastbourne". But accessibility had consequences. Ordinary people wanted to enjoy the seaside, too.

The sheer numbers arriving at the seaside after the advent of the railways led the Victorians to call with increasing urgency for new regulations to ensure strict public decency. One specific issue stood out: the danger posed for respectable families by indecent male bathing. A reliable summer feature of mid-century newspapers was the shocked expose, as it were, of yet another appalling breach of social standards on the beach.

This concern had first arisen at the start of the century. In 1813, Richard Ayton, a travel writer, reported that Swansea, despite its being "a fashionable watering-place", was witness to shocking scenes occasioned by so-called "bathing-sports": "While the ladies are walking on the sands, or waiting at the water's edge for their turn to be dipped, there is usually a parcel of naked men capering and roaring in the sea, who thus force themselves upon observation by startling both the eye and the ear".

This shameless male behaviour was fundamentally a matter of class. The Liverpool Guide had warned its readers back in 1799 that the "promiscuous throng of sexes and ages" taking to the sea "bids a great defiance to decency". The Guide was prepared to spell out that the "promiscuous throng"--by which the writer meant a mixed crowd of men and women--didn't comprise the local inhabitants ("to the credit of the town") but "families chiefly manufacturers from the interior". Now, in 1813, Ayton hoped to influence the behaviour of social undesirables by calling for the equivalent of a master of ceremonies for...