GATWICK TO LUTON passengers on Thameslink, and any combination between, from Monday 16 May, will be able to stay on the train as it makes it way underneath the Eurostar/Kings Cross/St Pancras complex ” a through train. Since last year the tracks have been closed whilst various works took place. Unfortunately, and due to the completely muddled thinking that is the rail industry, the actual St Pancras station has not been completed because to lack of funds and passengers for Kings Cross (400 yards) and St Pancras (600 yards at least) will still have to get off at the Pentonville Road - Kings Cross station and struggle along a narrow pavement and cross a busy main road. There is an (more or less secret) underground way for when it is raining and ABTN intends to survey the route over the next few weeks.
http://www.thameslink.co.uk