I want to book a one-way ticket on the Eurostar (Paris-London) but I see that if I book a round-trip, the price will be lower.
I am curious if I book the round-trip but only take the return leg, that my ticket will be cancelled. I am not sure if they ensure that every passenger booked on the train actually board it, and cancel the tickets of those who did not.
How does it work in that case?