Yes, before you ask, this is perfectly legal in the UK — you may legally photograph anything or anybody in public or on a railway station (and this includes children) without asking permission — the only exception is if a police officer considers you are photographing something pursuant to an act of terrorism. Moreover no-one except a police officer with a search warrant has the right to confiscate images or equipment or demand you delete images.
Surprisingly in all the years I've been quite openly taking photographs in the street and on stations I have only twice been harangued by a member of the public (both of whom thought I was doing something illegal — I wasn't) and twice approached by a police officer. Both officers agreed that I was doing nothing illegal, although one (who was armed) wasn't very happy as I was taking photographs near (but not of) some Arab embassies.
A few days ago I was sitting drinking coffee on London's Paddington Station and was close to the YO! Sushi bar so I couldn't resist photographing the chefs ...
Sushi Girl (left) and Sushi Boy
Paddingtom Station, London; June 2013