"ben doon" wrote in message
...
It comes from an old waste pipe from the bathroom, and is about 2"
diameter.
I can slap mortar in but the mortar will presumably slide into the wall
cavity behind. Do I stuff something in first (a bit of brick)? All help
gratefully received.

Since it's in the front of the house I'd probably remove the rest of the
exterior brick and make good with a whole brick (one that you saved when the
house was built). Failing that you can hawk a removed fragment around
looking for a good enough match.

Jim A