London 7 hours layover

How long do you think it will take to disembark your plane, go through the immigration line, take the 1+ hour taxi/tube/train to the center and walk to one sight. Then there's the 1+ hour back to the airport, and the recommended 3+ hour time to go through security, check-in and be ready to board? That sounds like a real challenge to see anything, to me.

Not much you can see in 30 minutes.

If you land on time, have no special delays at immigration you could be on transport to London by noonish. Arrival in London around 1. You need to be back to LHR by 230 to begin the process for security screening and exit protocol. That means you need to be on transport back to LHR by 130

Tantalizingly close but not practical

Not much you can do ; it could take two hours from getting of the plane going through Border control where there is usually a line and then a train or (if you got deep pockets) a taxi to the city. Then you have to leave London to be back at the airport by at least 3:30. Just an FYI the Big Ben clock tower by Parliament is covered in scaffolding for a couple a years.

go to Windsor

Once you've landed and cleared immigration I'd suggest finding somewhere you fancy eating in the terminal for lunch, followed by a bit of shopping or browsing and settling down for the last few hours with a good book or film. You don't have time to go to London.

Unless your flight is very early, there’s no way you will be in London by noon - 12.30 at the very earliest and possibly 1pm and that’s dragging your luggage with you rather than leaving it at the left luggage office. You would need to set off back to the airport at 1.15, so it’s not worth the risk of transport delays.

Windsor? Wow.

I would go to Windsor. It's 20 minutes by taxi.

Has the OP confirmed he’s landing at Heathrow then flying from there? Everyone is making that assumption but I can’t see it in the original post. Given that he’s arriving from Paris I did wonder if perhaps he’s arriving by Eurostar at St Pancras, which is of course actually in London.

Has the OP confirmed he’s landing at Heathrow then flying from there?
Everyone is making that assumption but I can’t see it in the original
post. Given that he’s arriving from Paris I did wonder if perhaps he’s
arriving by Eurostar at St Pancras, which is of course actually in
London.

Good points. We must await the OP's reply to see if we're wrong. In the meantime I've deleted my post which assumes the OP is landing at and departing from LHR.

he or she has said "next" flight so that sure sounds like a plane, and surely they would have said if it was a cross-London connection.

If that's what you want to achieve, gretter24, then you need to change the first flight to Eurostar, and the first one of the day.

You have to get to the Eurostar check in at Paris Gare du Nord a good hour before travel, but you'll go through both exit and entry border control before you board in Paris. At St Pancras International station in London you just walk off the train, through the zig zag corridors and out into the station and into London. It will be 8:32am (except Sunday, an hour later), so you can play until about 1:30pm including lunch before heading over to Heathrow for the fun and games there. You can leave your bags at St Pancras and return there to collect them and hop onto the Piccadilly Line for Heathrow.

That's a long but fun day.

Arriving Heathrow at 10:30, no way.

I wouldn't even consider it. Don't give yourself extra stress because something could go wrong. Take a cab to Windsor, what if there's a car accident or mechanical problems.

Stay in the airport, there's plenty of shopping, eating, and decent beer. You don't want to miss that flight back to the USA.

Stay in the airport. If you want to go to London you need another day.

"surely they would have said if it was a cross-London connection."

Only if they were aware that London has multiple airports, and knew they had to check tickets carefully. Flights to the US can leave from Gatwick or Heathrow, and now there are even flights on Primera Air from Stansted! I assume a flight from London to Paris could arrive at any of London's airports, depending on the carrier.

I read a story of someone who arrived at Heathrow, and when the driver asked "which terminal," replied "north terminal." Only then did he learn that London has more than one airport, and that his flight was leaving from Gatwick!

To gretter 24: Just agreeing with the others. If your flight to the US leaves at 5:30 PM, you need to be at the airport at 2:30 PM (not leaving for the airport - at the airport). So, that doesn't give you enough time to get into and out of central London from any of the airports, without taking a big risk.