London has a reputation for being pricey, but with kids in tow it doesn't have to be. Some of the city's biggest crowd-pleasers cost nothing at all, and a well-planned day can fill itself out with parks, museums and street spectacle before you spend a cent beyond lunch.
Start with the museums, because London's national collections are free to enter across the board. The Natural History Museum in South Kensington is the classic family pick — dinosaurs, a life-size blue whale and the earthquake simulator keep children of all ages busy for hours. Next door, the Science Museum packs in hands-on galleries built specifically for curious minds, while the younger crowd gets its own dedicated play zones. Over in Bloomsbury, the British Museum offers a treasure-hunt style visit: mummies, the Rosetta Stone and enough ancient armour to keep school-age kids engaged if you keep the visit short and focused.
Outdoors, the royal parks do heavy lifting for free entertainment. Hyde Park has boating on the Serpentine and the Diana Memorial Playground in Kensington Gardens, with a giant wooden pirate ship at its centre. Greenwich gives you wide-open space, the Meridian Line, street performers and river views, plus the chance to watch boats pass through. Regent's Park is a good shout too — you don't need a ticket to the zoo to enjoy its gardens and playgrounds.
Then there's the free street-level stuff that kids genuinely love: watching the Changing of the Guard at Buckingham Palace, walking across Tower Bridge on the public footway, riding the lifts at Tate Modern, or spotting street performers in Covent Garden, where acts run on laughter and voluntary tips. Borough Market counts as free entertainment if you graze rather than buy, and a trip on the Thames Clipper is cheap enough to feel like a treat even though it's technically transport.
The trick with free London is narrowing down. Pick one museum, one park and one spectacle per day, and build in snack stops — kids burn out faster than adults in the big galleries. Weekday mornings are calmer at the Natural History and Science Museums; weekends are livelier but the parks absorb crowds well. Most free attractions are walkable or a short Tube hop apart, so base yourself near a central line station and you'll rarely pay more than a few pounds to get around. Contactless payment caps mean public transport stays affordable too.
For families on a budget, this is what makes London work as a city break: the headline attractions are free, the add-ons are optional, and the best memory-makers — a playground pirate ship, a dinosaur skeleton, a guardsman in a bear hat — cost exactly nothing.