Eurostar is not an airline — it is the high-speed rail service connecting London St Pancras with Paris, Brussels, and Amsterdam through the Channel Tunnel — but it earns its place in this guide because it is by far the best way to travel between these cities with a Brompton. A folded Brompton travels completely free as standard hand luggage. No pre-registration, no bag required, no sports equipment fee. Just fold it at the station entrance, carry it on board, and stow it in the overhead rack or at your feet. The journey from London to Paris takes 2h15, London to Brussels 2h01. Far more pleasant than flying with a folding bike in a case.