Does the train for London pass over a railway crossing in Armoy County Antrim?

There is no train from County Antrim to London. Antrim is on the island of Ireland and London is in England on a completely different island.

Go back to the beginning, look at a map, and note that there is a large body of sea-water between Antrim and London!

Or are you asking about "Londonderry" - also called "Derry" - in Northern Ireland?

Unless to have mispelt L......Derry then wrong island

No.

You need to catch a ferry from Northern Ireland to various points in England and then a train.

Google "ferries Northern Ireland to England'

nationalrail.co.uk

If you think there are trains from Belfast to London you might want to glance at a map of the UK.

It did in the past. Dunno if it still does.

There are no trains for London in N. Ireland!