I didn't see anyone post:
7/6, UA 263, LHR-DEN was delayed, delayed, delayed, boarded, deplaned, and eventually cancelled for mechanical reasons (14:50 scheduled departure, cancellation about 22:00 and then going through passport control and luggage retrieval and taxi to a hotel we booked, etc.). Initially told it was mechanical, then it seems the crew timed-out.
on 7/7, same plane and crew was re-numbered as 3023 and flew the route to DEN.