Day 1 — Westminster & the South Bank
Start at Westminster. The Houses of Parliament and Big Ben (the tower, technically Elizabeth Tower) are best seen from Westminster Bridge or the far bank, where the whole facade opens up. Westminster Abbey is worth the entry fee if you have any interest in a thousand years of coronations and royal burials — book ahead, it's one of the busiest churches in Europe.
Walk through St James's Park to Buckingham Palace. The Changing of the Guard runs on a published schedule (not daily) — check before you plan your morning around it.
Cross back to the South Bank via Westminster Bridge and walk east. The London Eye, the Southbank Centre, and the National Theatre lead you towards Tate Modern, housed in a former power station and free to enter. Shakespeare's Globe is a few minutes further, with tours available even outside performance times.
Evening: dinner in Borough Market's surrounding streets, then a pub along the river or in nearby Bermondsey, which has quietly become one of London's best beer destinations.
Day 2 — The Tower, the City & the East End
Book the Tower of London for opening time — it's one of the most-visited sites in the country and the queues build fast. Give it at least two hours: the Crown Jewels, the White Tower, and a Yeoman Warder tour, which is included with entry and genuinely entertaining.
Walk across Tower Bridge (the glass floor walkway is a paid extra, skippable) and look back at the Tower from the south bank, then loop north into the City of London. St Paul's Cathedral is a ten-minute walk — Christopher Wren's masterpiece, and you can climb to the Whispering Gallery and beyond for views across the city.
Lunch somewhere around Leadenhall Market, a Victorian covered arcade in the middle of the financial district, unexpectedly beautiful and cinematic.
Afternoon: head east into Shoreditch and Spitalfields. Brick Lane for curry houses and bagels, Columbia Road if it's a Sunday (flower market), and the street art around Shoreditch High Street. This is the part of London that changes fastest — expect it to feel different from the postcard version of the city.
Evening: dinner and a proper pub crawl through Shoreditch. It has one of the best concentrations of independent bars in the city.
Day 3 — Museums & Notting Hill
Morning: the British Museum, free and vast. The Rosetta Stone, the Parthenon (Elgin) Marbles, and the Egyptian mummies are the headline draws, but the Enlightenment Gallery is worth a slower look. Two to three hours is realistic if you want to see the highlights without rushing.
Lunch nearby in Bloomsbury or Fitzrovia, both quieter and less touristy than the West End.
Afternoon: head to Notting Hill. Portobello Road Market (best on a Saturday, but worth a visit any day) runs through antiques, vintage clothing, and produce stalls, flanked by the pastel-painted terraced houses the neighbourhood is known for. Walk the residential streets south of the market for the quieter, more photogenic side.
Early evening: Hyde Park and Kensington Gardens, either renting a deckchair by the Serpentine or walking through to Kensington Palace.
Final evening: West End theatre if you can get a ticket — the TKTS booth in Leicester Square sells same-day discounted seats — or a final dinner in Soho, which stays loud and lively later than most of the city.