Verdict: 3 days is enough to cover London's core sights — Day 1 iconic landmarks + a West End show, Day 2 history and culture, Day 3 green spaces and Harry Potter. • Day 1 classics: Palace of Westminster & Big Ben (restored 2022) → Westminster Abbey → London Eye → Buckingham Palace (Changing of the Guard every Mon/Wed/Fri/Sun at 10:45) → Leicester Square → a West End musical in the evening (book early). • Day 2 history: Tower of London (built 1066, home of the Crown Jewels) → Tower Bridge → The View from The Shard (95 storeys, viewing deck on floor 72) → St Paul's Cathedral → British Museum (free, Rosetta Stone). • Transport: use an Oyster card or contactless card on the Tube; to save on sights, consider the London Pass (95+ attractions, 1–10 day options).