TRANSPORT: The offer is valid for bookings made before March 16 …
For spring, Eurostar is selling thousands of tickets for London (United Kingdom) from 39 euros. This promotion for travel between the 21st March and the 25th May and is valid for purchases made before the 16th March.
— Eurostar France (@eurostarfr) March 7, 2017
Exchangeable but not refundable
This rate is, moreover, valid for a round trip on several routes. 15,000 seats are planned for Paris-London route, 15,000 for London-Paris, 10,000 for Lille/Calais-London and 10,000 for a London-Calais/Lille, like Eurostar said on its website .
Bookings can be made online or in a Eurostar outlet. The ticket is not refundable but exchangeable before departure for a fee of 40 euros. With this offer, upon completion of payment, Eurostar also provides hotel reservations on Expedia platform with up to 40% off.