Thanks for confirming!
Pilot essentially said that Heathrow rejected the flight's arrival as it was too late (he announced it just after 11pm last night) and they weren't willing to grant an extension. I was curious what BA was going to put down as the official reason because the flight's delay was due to a late arrival from LHR (17:55 BA1702), which was also delayed due to a late inbound flight from VCE and an even longer wait at LHR afterwards (ATC restrictions, most likely? but the 20:30 flight to MAN departed a solid 30-45 minutes before the 17:55, which was stuck after being taxied).

Was hoping that flight crew timeout would have been a contributing factor but perhaps not - is there any chance I can claim compensation based on knock-off effects?