The radio station, which was also celebrating its first year on air, hosted the main stage where one of London's most-loved bands, Madness, performed.
Additional entertainment included catwalk shows, stilt walkers, roaming musicians, a ferris wheel, carousel and children's rides.
Two giant birthday cakes made of thousands of cup cakes provided a focal point, while outside Hamleys there was a children's lawn offering face painting, animal characters, a birthday tea party, balloon artists and magicians.
The event raised money to support Cancer Research UK's vital research into the prevention, diagnosis and treatment of cancer.
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