Metropolitan services on western part of the Circle

I have a question about services on the western part of the Circle line, the section between Praed Street Junction and South Kensington.
Originally this was opened by the Metropolitan Railway. I know that District trains were operated in their own right to Edgware Road (and sometimes beyond) from 1926.
I am wondering when Metropolitan Railway/Line trains stopped operating timetabled services to South Kensington, leaving the advertised services as Circle Line/Inner Circle.

I am somewhat surprised that I have never thought of this question before!