Back in 1969 I was in a crew returning from a 3 week VIP tour of the Carribean when we went U/S in Bermuda with an inoperative fire warning on the Stbd Engine. BOAC signalled UK with the part number and the time of that evening's BOAC VC10 departure from Heathrow to Bermuda. We had the groundcrew to replace and test the system and would be able depart on schedule.
We were there for 5 days and departed 2 hrs after the 4th firewire sent out actually arrived. One of the missing firewires reappeared in S America some years later.