I believe at one time, prior to WW1, maybe WW2, the Army & Navy store was restricted to members of the services and their families. They provided high class merchandise and they also specialized to have it sent anywhere where the British Army happened to be stationed. In these days all the top London department (Harrods, Debenhams & Freebody, Whiteley's, Derry & Tom's etc.) stores had departments to make men's and women's apparel (but also luggage or riding gear) to measure. They might have been somewhat cheaper then Savile Row, but probably not a great deal. Harold Nicholson might have had a good rapport with the people at A & N bespoke section. Other people would have used different stores or independent tradesmen. Since their heydays in Edwardian London, department stores have been in a permanent decline. Some have gone for good; others survived although most of the space gets franchised out to shops within the shop. (Today people buy designer names and are not happy anymore with everything bearing the store's label.) The Army & Navy store still exist, down in Victoria but is only a shadow of its former imperial glory. Part of the House of Fraser group of stores it is a non-descript middle of the road store, selling all the usual stuff you would expect. There is nothing as exotic as a bespoke department anymore (not in any London store).