Thanks so much for this information.
Looking with a loupe and your guidance, the maker’s mark is BB and then SL and a smaller D raised above the SL.
I have added some pictures … they are not the best !!
Very hard to capture on shiny silver
The maker’s marks are on the body of the teapot.
The Lion Passant and definitely an upper case O are on the inside of the lid of the teapot.
This teapot is part of a set: tea pot, coffee pot, sugar and creamer
On the bottom of the coffee pot: there is either an upper case R or A and Made in England
On the bottom of the sugar bowl and creamer: just an upper case A and Made in England
The A1 is on the bottom of the teapot – could just the bottom of these pieces be silver plate ?