Allegedly the Eurostar, which links Paris to London, does: "Inter-Capital" sets consisting of two power cars and eighteen passenger carriages. These trains are

Allegedly the Eurostar, which links Paris to London, does: "Inter-Capital" sets consisting of two power cars and eighteen passenger carriages. These trains are 394 metres (1,293 ft) long and can carry 750 passengers: 206 in first class, 544 in standard class > https://en.wikipedia.org/wiki/Eurostar#:~:text=These%20trains%20are%20394%20metres,class%2C%20544%20in%20standard%20class https://en.wikipedia.org/wiki/Eurostar#:~:text=These%20train.... I can't find info on the upcoming HS2. However I do testify that extremely long trains are common in Eastern Europe, Russia, India, etc. they might not be high-speed but they do move a lot of people at once.