But I was talking about 5 mins, not the odd 30 secs, which I think most regular travellers recognise (even if they don't like when it makes all the difference.)
But at Taplow it is possible to draw up in car by the gate to platform 4 and catch a train in under 30 secs.
But the principle remains the same is the time in public book the lat boarding time or the time the train starts moving which means the doors have to shut and locked before this time?