41% offBrunel Museum(£8.50 → £5) 27% offChelsea Stadium Tour(£30 → £22) 25% offTower Bridge(£13.40 → £10.10) 25% offDennis Severs House(£16 → £12) 20% offLondon Canal Museum(£7.50 → £6) 20% off Tower of London (£35.80 → £28.50) 20% off Hampton Court Palace (£28 → £22.50) 19% off Kensington Palace (£24.70 → £20) 18% off Foundling Museum (£12.75 → £10.50) 17% off Arsenal Stadium Tour (£30 → £25) 15% off (approx) English Heritage properties 14% off London Stadium Tour (£22 → £19) 11% off Sherlock Holmes Museum (£19 → £17) 10% off Westminster Abbey (£30 → £27) 10% off St Paul's Cathedral (£26 → £23.50) 10% off Churchill War Rooms (£33 → £29.70) 9% off Kew Gardens (£22 → £20) 7% off Leighton House Museum (£14 → £13) 6% off London Zoo (£33 → £31)
Shard, Madame Tussauds, London Eye, London Dungeon, Sea Life Centre, London Bridge Experience, Buckingham Palace, King's Gallery, Royal Mews, Cutty Sark, Royal Observatory, Up At The O2, tour of Parliament, National Trust properties, British Museum exhibitions, Tate exhibitions, Globe tours, HMS Belfast, Wembley Stadium Tour, Handel & Hendrix, Fashion & Textile Museum, Courtauld Galley, Dr Johnson's House, Chelsea Physic Garden, Postal Museum, Museum of Water & Steam, Crossness Engines (and the other London attractions I checked)