My copy of Fowler says that 'it was formerly customary, when a word ended in -s, to write its possessive with an apostrophe but with no additional s, e.g. Mars' Hill, Venus' Bath [...] In verse, & in reverential contexts, this custom is retained, & the number of syllables is the same as in the subjective case: Jesus' [...] not Jesus's. But elsewhere we now add the s & the syllable, [...] St James's not St James' [...]'
Perhaps St Thomas' are just being consciously old-fashioned.
This post was last modified: 19-01-2014 12:56 PM by robin orton.