So we get into our pre-booked seats. Everyone is reading and working. Just before the train takes off, two noisy teenagers burst onto the train and sit directly behind us. Almost immediately they start making calls on their cell phones and are generally as loud and as obnoxious as one would expect entitled teenagers to be.
I pointed out that they were in the Quiet Car--they hadn't reserved but had grabbed free seats, that you weren't supposed to use cell phones here, and if they wanted to do so, they could do so freely in every other compartment of the train. But please not here. The rules were clearly posted for everyone to see. There was also an announcement, but the girls were so noisy, they probably didn't hear it.
The teenagers rolled their eyes and ignored us and continued to be as noisy as possible. My husband and I spoke to them once again, with no result, and then went to report this. The only person we could find was the guy working in the snack bar who said he would report it to the person responsible. But nothing happened. Five minutes before we arrived in London, some ticket taker person speedwalked through our car without making eye contact, and that was it.
So basically it appears the Quiet Car runs on the principle that people respect the rules and behave themselves. However, if they don't, the train personnel will not get involved in any useful way.
Would it do any good to write a letter of complaint? We definitely did not get the "service" we thought we had paid for.
The way back, fortunately, was quiet. Luckily everyone was on the same wavelength about the quiet business as we didn't see a single train employee--they checked our tickets on the platform before we boarded.