If you're number 1 to depart at CTOT -5 (and note that doesn't necessarily equate to arriving at the holding points first) then you'll go at CTOT -5. But there are a shedload of factors which decide where you are in the sequence including start times, route, delay already taken (on stand or remote), relation to other traffic types/speeds/climb performance, type and performance of the landing aircraft between which you're going, etc.etc. If you're LGW based, come and visit us....speaking personally, there are some airlines I'll very rarely try to depart in a tight gap because I know they'll be slower to roll than others even when told to be ready for immediate
