St. Pancras to Heathrow—how long?

Take the train that gets you there at 9:30. You clear border control and security at Gare du Nord, so make sure you are there 1 hour before departure time. These days, you should plan to be at the airport 3 hours before flight time.
And it is the Eurostar. Eurail is the consortium that sells railpasses to people outside of Europe. Needless to say, the Eurail pass is not valid on the Eurostar trains.

Hi,

You're in Paris the day before. When you leave Gard du Nord to catch the EuroStar, you go through French Immigration since you are exiting the Schengen zone. The Tube schedule is accurate, one hour from Kings Cross to Heathrow. I've done it.

No way I would take the Eurostar to London the day I'm flying out on a trans-Atlantic flight! What do you do if there are delays with the train and you don't make it to Heathrow in time??? If you're okay with the idea of buying a new walk-up ticket to get home, then it's okay. But otherwise no way I would risk it. Eurostar (not Eurorail) has had too many problems over the past year in Calais to make this a good idea.

Spend your last night in London.

If you are going to Heathrow, best go there directly.

You don't say with which airline you are flying back with - if it is British Airways they would through-check your bag from Paris even though you are on two separate tickets. Strictly speaking you would not be protected in the event of a mis-connect but BA policy is to change your onward flight if possible.

If you are going with someone else then if you have checked bags then it is less convenient as you would need to collect them. If you only have hand baggage then you can still connect airside.

If going the night before rail comes back into the equation as a possibility. There is no custom check between EU countries, and on Eurostar you go through UK immigration in Paris, although they can decide to check again on arrival.

Oh yes, my mistake, I did know it's Eurostar.

I am flying home on Virgin. There IS a flight from Paris to London in the morning, on British Airways. My only hesitation is it gets into Heathrow at 7:45, and my flight doesn't leave until 1:40. I'm sort of dreading having hours of hanging out at Heathrow until my flight leaves.

Unless there are fantastic things to do inside Heathrow airport??? :)

Thanks for your replies, they have been helpful! Not sure yet what I will do, but your information has helped.

There are multiple flights from Paris to London every day that will get you there before noon, not sure why you think there is only one.

I would plan on spending the night in London or near Heathrow (as others have suggested). Take an evening Eurostar into St Pancras. If there are any issues with the train you choose you have multiple other options as backup including a plane if all else fails which still get you there in time to make your flight home.

Yes, the tube ride from St Pancras to Heathrow is an hour and is a straight shot with no transfers, I've done it multiple times myself. There are multiple nice hotels located around the St Pancras station, even a couple located inside the station, so spending the night there and then taking a morning tube to the airport should work fine and be a lot less stressful than hoping your Eurostar isn't running late.

On a weekday there are 3 flights that arrive at Heathrow from Paris in the morning around 10:30-11:00 - BA and AF from CDG and BA from ORY.

There is also a BA flight from ORY that arrives at 8:35.

Your choice may be more restricted at the weekend.

Marco, I'm flying on a Sunday. I found another flight that gets me there an hour later...but I'm thinking I will just sleep in London instead of Paris. One more morning run in London before I leave for home! :)

Just to give you an example of the possibility of a delay on the Eurostar - I traveled the opposite direction last Fall. At St Pancras, they announced that there was a delay in departure due to a cable theft on the line. The train left about 10 minutes late but got in to Paris 101 minutes late as the train apparently could not use the high-speed tracks on the way.

Follow the advice as others have said. Too many things can cause delays.

stay in London - take the Eurostar and stay at the great northern at kings cross- you can then take the tube directly to lhr and its an easy off from the Eurostar. if the great northern hotel is too expensive there is a premier inn around the corner.

"I'm sort of dreading having hours of hanging out at Heathrow until my flight leaves."

These days with airports, you can either be panicked or bored. For a "high risk" flight like this one (London to the US), where missing the flight will cost you a LOT of money, I'd go with bored. Get to London the night before.

You need to plan to be at Heathrow 3 (yes three) hours before your flight. The only way I would take the Eurostar is on the very first train of the day, anything else is too close. (My Eurostar to Paris Sunday was about half an hour late. Not bad but with your plan it could have been.).

Personally I will be returning to London this Sunday morning for a flight that's at 16:00 Monday. (Plus its strike season in France. This gives me a pad)