The Tube is the fastest way to get around London. It runs from approximately 5am to midnight (later on Fridays/Saturdays on some lines).
Payment: Use contactless bank card or Oyster card. Never buy paper tickets — they cost double. Daily caps apply automatically (Zone 1-2: ~£8.10/day).
Tips: Avoid rush hours (7:30-9:30am, 5-7pm). Stand on the right on escalators. Mind the gap between train and platform.
Step-free access: Check the TfL website for step-free stations if you have pushchairs or mobility needs.