"The smell of the sea at St. Tredennick"

There are two Tredennicks, both in Cornwall (Tredennick, St. Issey, Wadebridge; Tredennick, Liskeard), but neither is on the sea and neither is referred to as "St." Tredennick.

Nor does the Catholic Church recognize a "St. Tredennick".

I am assuming the location is a Christie invention.