There is a moment at the beginning of Lord of the Flies where the shipwrecked children realise that the adults have all been lost and they can now descend into savagery. Much the same thing has happened sartorially in the House of Lords since the hereditary peers were expelled. The thin veil of civilisation has been ripped aside and now anything goes. Ties are optional, with Lord Davies of Brixton saying, in that snobbish way reserved to socialists, that nowadays they are only worn by ‘estate agents and funeral directors’. I was delighted to see Baroness (Joanne) Cash pointedly wearing a tie at the despatch box the next day.

Sir Hardy Amies, Queen Elizabeth II’s dress designer, once said: ‘The way you dress is a mark of the respect in which you hold those people you are going to meet that day.’ The hereditaries knew that, hence Viscount Goschen’s one-and-five-eighths inch turnups, the 8th Duke of Montrose’s beautifully cut black suits, Beano Mancroft’s hunting tie-pin, the Earl of Minto’s elegant but understated Turnbull & Asser ties, and the shiny toecaps sported by Earl Howe, the Earl of Effingham and Lord Reay. In their place, we now see trainers (and not just because of gout), brothel-creepers, black shirts, bootees, light corduroy jackets and even ski jumpers. Now that the immaculate Viscount Thurso has gone, the Lib Dems look a shower. Bishops who wore sandals are now veering dangerously towards flip-flops. A former prime minister has taken to wearing elasticated black moccasins (and it isn’t Theresa May). There has been a sorry outbreak of light grey socks on the Tory privy counsellors’ bench, unthinkable in the days when Lord Trefgarne graced it. A life peer who will remain nameless, but can be heard on Times Radio on Friday mornings, has taken to wearing very light grey suede lace-ups and elasticated trousers. Lord (Dominic) Johnson was upbraided by a colleague when he turned up wearing a blazer, with the words: ‘We don’t wear metal buttons in the Chamber, old boy.’ The brass buttons feature his (rather magnificent) coat of arms, and he was golfing later that afternoon, but these rightly weren’t considered excuses.

There are about a dozen former Commons chief whips in the House of Lords, including The Spectator’s editor. (The collective noun for chief whips is ‘a lashing’.) They tend to dress properly, as do Old Labour peers such as George Robertson, Des Browne, John Reid and especially Alan West, who wows their ladyships at the State Opening by wearing his full-dress admiral’s uniform under his ceremonial robes.

My new book has taken me to Napoleon’s marshals’ battlefields in eight countries, but this time I’ve largely manumitted my long-suffering wife Susan from having to come with me. The day after we got engaged, I took her to where Mussolini was shot at Lake Como; on our honeymoon we went to a Japanese concentration camp in Thailand and a 90ft tower of skulls in Cambodia. I’ve since taken her to Auschwitz and Stalingrad and to see a two-headed foetus, the result of Agent Orange, in Hanoi. Never say I’m not romantic. For this book, however, I took her only to the battlefield of Barrosa in southern Spain, where Marshal Victor was defeated by an Anglo-Spanish-Portuguese force in 1811. Mansplaining to her as we drove there about the importance of topography, and how military historians not visiting battlefields was like detectives not visiting the scene of the crime, I looked slightly idiotic once we arrived to discover that the battlefield had been turned into a golf course.

I was once approached in a Miami bookshop by a woman who wanted me to sign my biography of Winston Churchill to Winston Churchill, claiming she was the reincarnation of the great man. I first checked she wasn’t packing heat – you can never be certain in Florida – before asking her some questions about the Admiralty’s handling of the public relations around the battle of Jutland. Her answers made it quite clear that she was not the reincarnated Churchill, but I’ve always wondered how I’d have reacted if she had given me an answer regarding the post-battle cables from David Beatty and John Jellicoe that only the real Winston Churchill could have given?

I was intrigued to discover that one of the ways that the House of Lords staff spot when peers have gone gaga is when they wander around with their trouser zips undone. The doorkeepers have a quiet word with the whips, who then gently inform the peers’ families. From Lord of the Flies to the flies of the lords.