Another facet of your many interests. I have recently been pondering a Raleigh three speed, but it would involve a lot of adjustment, mainly psychological, after being spoiled by riding an older Colnago Master. I am also hesitant about returning to a Sturmey Archer on Austin's hills, not that 53/42 by 12/21 was easy!I'm an avid cyclist. Having built bikes from the frame up with vintage and period-correct componentry (gruppos), I can assure you that chain guards that cover the top of the chain do exist but are a bit of a mixed blessing. They protect your trousers from grease, but they make getting at the chain for repairs (removing links, tightening the chain, etc.) a harder task. Even the seasonal cleaning of the chain with a lube (like White Lightning) is tedious with a guard.
Now the fully enclosed chain is often found in vintage Raleighs, Humbers, etc. They look very retro and nice. But these chain cases are, of course, much more of a pain to remove. I have three Raleighs in my stable (two Superbes and a Sport) and I wanted a chain case for one of them, picked up in the after-market. I was persuaded not to do this by my local bike shop chap, who said they were hard to maintain.
My solution is simple and elegant (sort of, LOL). I use trouser clips or else tuck the tops of my trousers into my socks. I also roll up the right trouser leg since this is the side where the chain is. Most of the summer, I wear shorts for distance cycling, so it is only of concern when I have to wear trousers. If I must wear a suit, I have an even simpler solution: I drive!