Team 002: The Abduction of the Queen

Tom Carter is 11, lives in London and is just a regular kid, until one day when he climbs into the garden of his neighbour. Everyone thinks she's just a frail old granny, but when Tom tries to nick a piece of cake, he gets caught -- and discovers that this little “granny” is anything but frail -- and that she has an amazing secret.
Because her name is Gertrude.
Granny Gertrude. Agent 002.