London’s major national museums are free to enter, climate-controlled, and in summer — when the usual school trip crowds thin out mid-week — some of the most peaceful places in the city.
The National Gallery on Trafalgar Square: one of the great permanent collections in the world. On a hot Tuesday afternoon, you can stand in front of a Vermeer with almost no one beside you.
The Tate Modern: the turbine hall alone is worth the journey — vast, cool, and home to a series of extraordinary commissioned installations. The current summer show is worth building a morning around.
The V&A in South Kensington: the finest decorative arts collection in existence, with a courtyard garden that functions as a quiet outdoor room when the temperature allows.
The Natural History Museum: the Central Hall — with its blue whale skeleton — stays naturally cool and remains one of London’s most architecturally dramatic interiors. Good for all ages, particularly good for escaping the afternoon peak.
The Wallace Collection in Hertford House, Manchester Square: London’s best-kept secret for art lovers. Smaller than the national collections, quieter in summer, and the French furniture and armour rooms are as cool as anywhere in the city.