As part of a 3 week trip, I plan on traveling from London to Geneva via Eurostar to Paris. I am getting a 15 day Eurail pass. I know it is not valid for the Eurostar, but I want to get the passholder discount for the Eurostar. I've read that I have to have an "active" Eurail pass in order to get the passholder discount. Can I activate my Eurail pass in London when I board the Eurostar?
book your eurostar ticket at the same time you order your pass. it will most likely be at eurail.com
You may do just as well price-wise booking a regular ticket at www.eurostar.com. (You cannot book a passholder fare at the Eurostar site.) However, you can book a passholder fare at www.raileurope.com. Or you can call the Eurostar office in London. Dial 011 (international access code for the US and Canada) + 44 (country code for the UK) + 1233 617 575. For expert and free advice (much better than mine), call Budget Europe Travel Service (800-441-9413).
book at www.raileurope.com there you can book your eurostar ticket also.