1st class trains are actually pretty common on medium-distance train services into London (in contrast with the author's examples, first class on British trains is often barely distinguishable in terms of comfort from standard class to the point where you wonder why anyone would bother to pay for it)

1st class trains on the London Underground would be hugely unpopular because deliberately running overcrowded services below maximum capacity to skim a bit more money off the top is seldom popular, especially when no commuter is naive enough to believe they'll be compensated for the extra wait and crush with reduced fares.