4 Gilston Rd., South Kensington
Established in London in 1918 by a Japanese immigrant, the Budokwai is still regarded as London's premier martial arts club. Don't let this intimidate the little ones—the juniors classes are particularly great, and in addition to judo, Budokwai offers karate, aikido, and jiujitsu for all levels from beginner to master. Kids are taught carefully, and judo teaches more than just fitness: Patience, discipline and self-defense are among the other qualities gained.
Stella McCartney Kids
91-95 Fulham Rd., South Kensington
Stella's latest outpost includes a Stella McCartney Kids section complete with its own entrance. You'll find plenty of "mini me" versions of pieces from the women's collection, along with other really bright and modern picks. It's worth having the little ones try something on, as the fitting rooms are seriously fun.