According to Burke, south London was well served but Kensington, Mayfair and St John's Wood were to be avoided by anyone likely to be taken short. Nearly 30 years later, Jonathan Routh published his first Good Loo Guide and in the 1987 edition he emphasised the rapid decline in the number of London's loos.
It has got worse. Few tube stations now contain a convenience - Harrow on the Hill is an honourably rare exception - while councils everywhere simply padlock their loos and mutter about economies. One or two have actually "privatised" the buildings and sold them off. Approach one of those distinctive cottages in an emergency and you may well find an irate estate agent barring your way.
Some capital conveniences survive, particularly those at the Wallace Collection which retain the wonderful tiles once found in Sir Richard Wallace's Smoking Room. Outside the Norwegian church in Rotherhithe, helpful signs include the Norwegian equivalents of Men and Women for the benefit of the Scandinavian sailors who once patronised the nearby Surrey Docks.
And until recently I recommended a trip to Harrods, but they have got wise to interlopers and now charge an exorbitant fee, as well as turning away anyone not suitably dressed (darling, how do you dress for the loo?).
Others are literally museum pieces, notably the conveniences which once graced Kingsway and were famous because the attendant kept goldfish in the cistern. They now reside at the Museum of London.
But perhaps the most interesting after-life occurred on Shepherd's Bush Common. The loos were built for the benefit of the crowds on their way to the 1908 London Olympics at White City. Today they house a snooker club.
In other words, if you see someone scurrying across the Common with questionable urgency, don't assume the worst. It is probably Steve Davis or Jimmy White on their way to practise.
Andrew John Davies
The loos/snooker club are on Shepherd's Bush Common, W12