It appears to have been taken over by the Royal British Legion in 1926. I don't know what it was before.

The building is a duplex; its left half, which I think is called "Pepys House", is I think an ordinary house; its right half, which I think is called "Pepys Hall", is the British Legion Hall. My _guess_ (on the basis of looking at the brickwork facing the street, which has obviously been substantially modified) is that before the RBL took it over in 1926 both halves were houses. And my _guess_ is that when the building was originally constructed it was as two houses. But those are both mere guesses.