Me and ds are off to London in Feb for a few days. As he is obsessed with the tube we will be mainly tube riding across the 3 x days. He is 9 so I believe under 11s travel for free, however please could you let me know if there is a cap on adult travel costs per day? I fully expect to be travelling on every tube line across all zones so I want to understand whether I could purchase something like a day rider which would work out more cost efficient for me? I know some of you lovely mumsnetters will have the answer for me. Thanks in advance ☺️