Clearing customs

Eileen, You'll be processed by French Passport control prior to entering the departure area at the EuroStar terminal at London St. Pancras, and I'm assuming by British Passport control at Gare du Nord in the other direction. You MUST check in for the EuroStar at least 30 mintues prior to departure, but I'd allow a bit more time. Happy travels!

Well, you need to clear Security and Passport control but not Customs. You will clear Customs upon your return to your first port of entry to the U.S. (unless you are coming from Ireland where U.S. Customs does the check there - very slick and handy). You've already cleared Customs entering the EU - once inside the EU all is just a big love-in, well, unless you factor in the VAT. If there's something you really want from Europe, say oh, perfume or a Gucci scarf. Check out the price of that item here first either on line or in a store. My favorite perfume is 25% less purchased on line here than in Paris - go figure:) (It isn't as much fun however buying it via Amazon...poo).

Ken is 100% right.
Marie misread your question.

While both The UK and France are part of the EU, the UK is not part of the Schengen agreement. There are complete border controls between the UK and France. In London, at St Pancras, you can expect a queue to check in, then airport style security check for you and your bags (often with sniffer dogs), then a UK passport check, a French passport check, and a Customs check. If you have anything to you have to go through the red channel, if not you go through the green channel. Then there's a large waiting area until your train is called. When your train is called you go up the moving ramp and board the train. On arrival at Paris you just get off the train, walk to the front and enter the Gare du Nord station, and you are in Paris!! As Ken says, you need to be checked in an absolute minimum of 30 minutes prior or you don't go. That doesn't mean to be in the queue to check in - it means through the check in barrier and in the security queue. The cut off is strictly enforced in both directions. I advise 45 minutes to an hour ahead for comfort, depending on time of day and time of year. At Paris, for the trip to London, I have seem much longer queues for check in, and much slower transit through the checks. I will never arrive at Gare du Nord with less than an hour again - it is just too stressful. At Paris, you have to go up an escalator to check in. After check in and security it is the same stages as in London, but expect more probing questions from the UK Border Officers, and again, if you have items to (that is certain specific items or purchases above your allowance) it is the red channel for you instead of the green one. When you return to the US you will have Immigration and Customs (and Ag inspection, too) into the US at your arrival airport in the US.

Many thanks to each of you for responding. Taken together, you've really answered all the nuances of my question. Eileen

One step not mentioned is that you will need to complete a landing card in the Gare du Nord for handing in to UK immigration.

Thanks, Marco - I had that in my mind while I was writing and it never made its way down to the fingertips.... oh well. good catch