Sykes-Fairborne knife question

[Garth Thompson]

This knife and leather scabbard came in the lot I recently acquired. It appears to have a cast handle and has a broad arrow proof mark. It looks to have been well used and the blade sharpened. What I know about these knives is pretty limited so any help appreciated.
Garth

[nickn]

Ww2 issued 3rd pattern with wrong sheath