DH and I will visit London from the U.S. in late August. We are thinking about taking a day to travel to Cardiff to see the Doctor Who Experience and add with Cardiff Castle or the National Museum of Wales if time permits. We'd love to hear from our UK friends on whether the Doctor Who Experience is worth the long trip out from London. We'll be in London almost 12 days and I've planned full days with only one day left to plan. For now it's being left as an "anything that we missed so far" day but if going to Cardiff for the day is worth it, I'll pencil that in. As a point of reference, my daily commute to work is 2 1/2 hours each way via commuter rails and subway and so the train ride to Cardiff is fine as long as the destination is good. Thanks for any feedback you might have.