I haven't visited London in years, but I'm booking a trip for myself and my elderly mother for her birthday in May. I have tickets booked for the Duchess theatre in the evening and we plan to arrive in London at around 1pm that day. She has mentioned that she would love to see the National Portrait Gallery and we are staying overnight, so could possibly do that the next day. So - she is pretty mobile but can't walk very very far without a sit-down, and I'm not sure she will cope with the Tube (??). What I suppose I would like are recommendations for a decent hotel near the Duchess (easy walk) and then the best/cheapest way to get to the gallery and back the next day. I am confusing myself Googling! TIA.