Sunday Times crossword editor here. Apologies for the repeated crossword - a mistake I hope not to repeat. If you think the chess puzzle is a repeat too, are you able to give me an idea when it was used before?
Perhaps a better idea re your Chess enquiry would be to enquire from a Chess site rather than a Crossword one.
I hope that this answer will not preclude my chances of success in the future,in my entries to the Sunday Times Crossword.