Some TOCs have a policy of despatching as soon as the train is ready at stations very close to London Termini, that may be the case at Finsbury Park.
If that is true then the other dispatchers are breaking the rules then! Any trains that arrive early will be held and leave dead on time. As such, many Moorgate services wait a minute or two before going (platform 1) - while a lot of trains to King's Cross (on platform 2) will be dispatched quickly as they're invariably a minute or two late.
It's good there too, as a lot of people are trying to board these trains. It's not a station where you could argue that trains could possibly become set down early.
