The Apostrophe in St James’s

In British English, the park is traditionally known as “St James’s,” following the rule of adding an apostrophe plus an “s” to the singular possessive form, even when the noun ends in “s.” This form, preferred in British publications and formal contexts, reflects the historical and official usage.

In American English, the traditional British spelling “St James’s Park” is widely used and recognized due to its official status.