After a signed copy of HONOUR OF THE KNIGHTS as a present for Christmas? If so, there are a number of branches of Waterstone's stocking them:

Brighton
Camden
Canary Wharf Cabot
Canary Wharf Jubilee
Finchley Road (O2) (Sold Out)
Gower Street
Greenwich
High Holborn (Sold Out)
Islington
Kensington
Leadenhall
Piccadilly
Trafalgar

A signed copy of the novel would go down well as a stocking filler or as a Secret Santa gift for that difficult to buy for work colleague!