London doesn't have traditional German-style markets, but it has big Christmas events from mid-November.
- Winter Wonderland in Hyde Park: rides, market and ice rink; you need to book entry in advance, even for free time slots.
- Southbank Centre Winter Market: along the Thames near the London Eye.
- Covent Garden, Regent Street and Oxford Street: beautiful free Christmas lights.
- Leicester Square: a small central market.
Note: on 25 December almost all London Underground and bus services stop; plan to stay near your hotel that day.