Hi Dan
This answer may not be entirely accurate, but a £10 Christmas Bonus was first awarded to Pensioners (only) by Ted Heath when he was PM, so early 1970’s! What I do know is that he wanted to introduce it, but the Civil Service were against it for all sorts of admin issues. So he just announced it (unannounced, as it were) during a live Party Political Broadcast. It happened late, but it happened.