Tradition is that seafood, particularly oysters shouldn’t be eaten unless there’s an ‘R’ in the month, clearly that precludes the summer months of May through August.
Perceived wisdom would have it that this tradition is based on common sense, that seafood was more likely to spoil in the hot summer weather, especially in the days before refrigeration. Indeed Henry Buttes, an Elizabethan cookery writer wrote (in 1599) “The oyster is unseasonable and unwholesome in all months that have not the letter R in their name”.
However, in more recent times there’s a more prosaic explanation, which might explain why the phrase is still so widely known:
In Victorian times, when city dwellers first started to take holidays, the furthest most would travel would be ‘to the seaside’ and for the poor of London’s East End the seaside meant Southend on Sea, some forty miles east at the mouth of the Thames estuary. The modern railways meant that Southend was reasonably accessible for ‘eastenders’, similarly Whitstable in Kent famous for its oysters.
Like Whitstable, Southend, and more particularly its suburb of Leigh on Sea has long had a thriving seafood industry, Leigh’s cockle sheds remain a local tourist spot.
The potential impact of tens of thousands of hungry Londoners on local seafood stocks would have been devastating, so the local fishermen made sure that tourists were reminded of the ‘R in the month’ rule and were thus dissuaded from helping themselves to the wealth of local mussels, cockles and prawns.
On a positive note, Whitstable and the Essex town of Maldon both hold an annual Oyster Festival at the start of each September to celebrate the return of Oysters to the market.