ARWadsworth wrote:

Maybe, but I have never come across 4BA threads on on backboxes in
houses where the original lighting circuit has an earth. ISTR that
lighting circuits needed an cpc from 1966 onwards.

This did have an earth, not sleeved though. It was a bakery not a house.
Building dates from 1936.

--
Dave - The Medway Handyman
www.medwayhandyman.co.uk