Trewins joined the John Lewis Partnership in January 1940. It was one of fifteen department stores which had previously formed the Selfridge Provincial group of shops owned by the American businessman Gordon Selfridge. He sold the group to the Partnership and returned to America to escape the harsh conditions and trading problems being experienced in Britain.
The acquisition of the SPS stores was to be the saving of the Partnership as, in September 1940, an oil bomb dropped onto the main Oxford Street shop causing such damage that the building had to be demolished.
Following the bombing a letter was sent out to all account customers advising them of the damage to the flag ship shop and encouraging them to shop at the other branches – which of course included Trewins!