Extending Duty Period
This may be quoted as a Commander's say, but this is where good CRM comes into play. If the other cockpit & cabin crew disagree, the majority makes the call (this from an old and distant crew rostering boss who was involved in the original CAP371 overview and implementation), this flight safety after all.
Sometimes a NO is commercially unacceptable, but heck we still have crew and punters alive. I ask you to argue against flight safety, and justify that argument.
PS. Yes the original CAP371 and modified BALPA industrial documents.