Hugh Riddle

Yes, forgive my toying with unbroken smoke and fire protection using the existing 10mm wide rebate, beyond the already met proportional requirement. The batwing strip seems to need a wider, deeper rebate. I've added the link I forgot to give to my last reply.

Very many thanks, Neil, for your precise and comprehensive response and troubling to indicate the standards concerned. BTW, I've spotted an approved intumescent tape with an edge smoke brush. Might laying a strip downward across one leaf of each hinge be worthwhile, to minimise smoke and fire passage? https://www.amazon.co.uk/Intumescent-Self-Adhesive-Draught-Excluder-Approved/dp/B0DRFQH49T?th=1

The seems no systematic/designed solution ,to stop smoke passing through most fire-rated door hinges: between the leaves; through the spaces between the leafs and the knuckle (see white wire in .jpg below); around the knuckle. I can't find a fire-rated smoke seal for hinges and can only imagine a fire-rated adhesive foam - similar to a window draught excluder strip. BTW please, how far should the knuckle or its pin best be positioned from the jambs?