One of the best is about Victor Legg, switchboard operator at the Ritz, who late in the evening of August 31, 1939, put through a call to a guest at the hotel, a man so offensive that waiters bribed each other in order not to have to serve him: Randolph Churchill. Legg listened in, and heard Churchill be told that Germany was about to invade Poland. When Legg dialled the BBC moments later to share the intelligence with them, someone came on the line — presumably from MI5 — to warn him to keep what he had heard to himself. When he finished his shift he walked to Soho to an all-night café and, as Mr Sweet puts it, drank coffee, smoked Craven "A" and ate a bacon sandwich until the rest of the world knew what he knew.

While this book is about grand hotels, it is also partly about the high end of the underworld that frequented them — a subject of enduring interest, perhaps because of the image of the spiv that remains redolent of World War II. We meet all sorts of conmen, including a genuine baronet who tried to sell bogus commissions, an officer who impersonated one of a higher rank and shot himself in a hotel lavatory, and shop-girls passing themselves off as aristocrats in an age when having a title (or professing to have one) was enough to make even the most rational of third parties suspend disbelief. These hotels were also packed with enemy aliens, many of whom were rounded up and sent to internment camps, often with the fascists they despised. They had their share of abortionists, prostitutes and adulterers; while downstairs in the public rooms there were men in uniform, or men in dinner jackets, dancing with their wives — or other men's wives — to the dance bands that for many epitomise the era. Lewis Stone, one band leader whose widow was interviewed by Mr Sweet, used to leave pauses in his music for the distant banging of bombs to fill in.

The attraction of the period is, I suppose, that this was an age less regulated (at least until war, and the clampdowns that it brought), and more irregular, than ours. In an age before health and safety, one of the chefs in a grand hotel decorated his dishes by spitting the garnish on to it. Then there is the entertainment of watching how human nature copes with a sudden crisis that turns everything upside down. Rationing was slow to make its impact on some hotels; others offered a rehydrated egg omelette that was deemed almost inedible. Perhaps our affection for this period is because we have grown up with stories from parents and grandparents about it. Or perhaps it is that so few of us who remain had to live through it.