Travel from Paris to London

Definitely the Eurostar. City center to city center in less than three hours. (When the high speed rail link on the UK side is completed, the trip will take a little over two hours.) Fares vary widely depending upon time of day, day of the week, and how many disoount seats are left. To get the best fares, book as far in advance as possible at www.eurostar.com. Be aware that sometimes return (roundtrip) tickets are cheaper than single (one-way) tickets. If that's true for the date you wish to travel, book an arbitrary return date and throw away the unused portion of your ticket.