Three are giving customers free access to tube wifi in the coming weeks.
It's already in place and is provided by Virgin Media (also free for their customers). Rolling out to three customers in the coming weeks.
It's only in stations - not in tunnels between stations - however I've found this is long enough to send messages by whatsapp etc if you need to get in touch with people on the ground.
Another quality freebie from three and makes up for the times when you can't call or get online despite having full bars and 4G signal.
Maybe not technically a deal but as equal to a deal as the roaming offers.http://blog.three.co.uk/2014/07/17/three-offers-wi-fi-london-underground/