Oyster Card question

[hornet]

For anyone who uses them more than I do and understands the bloody things....

I get the whole touching in and out bit, but what happens when "in" is on the Underground but "out" isn't? I need to get to City Thameslink from Euston Square, so I'll hop off the Met and onto Thameslink at Farringdon, is that one journey (if so, what fare?), or do I have to do assorted touching in and out at Farringdon, even though there are no barriers between the Underground and Thameslink platforms? Help!

[LittleBro]

There is actually an Oyster touch point on the flatform at Farringdon but you dont need to touch it.

Going from Kings Cross to City Thameslink is one journey (even though its a mix of train/tube) which you pay just once for. I think its £2.00 peak, £1.50 off peak.

[Simpo Two]

In a similar situation (I won't bore you with the details!) I got stuck at the turnstiles leaving the Underground so I just followed somebody out through the disabled barrier, which is very wide and stays open a good long time