It was the last of the hourly services so no impact by holding the train.
If the Donkey unit goes up late, then it’s late locking in on the Bourne End - Marlow section and therefore the Maidenhead - Bourne End shuttle runs late.
While the Marlow portion has long turnarounds and therefore plenty of recovery the Bourne End does not. No risks can be taken with its performance whatsoever so the maximum hold we’d allow on the 1637 Marlow is a lot shorter than simply looking at its turnaround would suggest.
It’s also typically proportionally very busy with passengers starting their journey at Maidenhead, so needs of many vs few comes into play in the policy too.
Regrettably it looks as if your Didcot on that day has only just missed the cut-off (5 is the longest hold I’d allow), but we have to be ruthlessly consistent with application of holds policy; as it causes problems if one person authorises 10 minutes one day and the next controller the next day refuses the same connection delay because it’s outside the 5.