18-hour layover in London

To be honest, if I were you I'd stay somewhere closer to Heathrow and not in London. That way you can check into your hotel, freshen up, and gauge your energy level for a trip into London for dinner. If your flight is late for any reason, a near-airport hotel will really make life easier. Plus, in the morning you will have a quicker, simpler trip to the airport to check in for your flight and pass through security.

As far as what to see & do in London for a short time on a summer evening, the Westminster underground station puts you by Parliament Square with a view of the Houses of Parliament, Westminster Abbey, and the London Eye which might be nice to see at sunset.

What do you mean by London Kensington? Is that a particular hotel, the general area?

If you are staying in the Kensington, Earl's Court or South Kensington, you should estimate your hotel arrival an closer to 5:30 or 6:00 PM

We are staying at Kensington, Earl's Court. We also will not have baggage (checked all the way through) - we will have our clothes/toiletries for overnight in our carry on luggage.

Kensington and Earl's Court are two separate neighborhoods. Just because they have either in their name doesn't mean they are acrually there.

What is the name of your hotel. Or the address. No hotel is called Kensington Earl's Court.

Is it the Premier Inn?

If all goes well you may be in the city by 6! Cross your fingers...I've gone through customs at Heathrow in as little as 15 minutes...other times it's taken closer to 90 minutes. If you want to maximize your time further, take Heathrow Express into town rather than the tube or a cab. It's 15 minutes from the airport to Paddington Station. If you buy tickets ahead of time they aren't terribly expensive. Might be worth it in your case.
On one of my trips there this past year I had a layover similar to yours. I got into Heathrow around 2 and my flight out was midday the following day. I took Heathrow Express into town and then a taxi to my hotel near Victoria Station since that's where I needed to catch the Gatwick Express to that airport the next day. I had plenty of time to walk past Buckingham Palace, through St. James Park, up to Trafalgar Square, have dinner in Covent Garden, then walk back to my hotel as the sun set. Went to sleep, caught the Express the next morning, and took off for home. It was a nice evening in the city!
Once you let us know specifically where you are staying we can make suggestions for how to make your short time there enjoyable!

Yes - I believe the Premier Inn. This is the address: London Kensington (Earl's Court), 11 Knaresborough Place, Kensington. The reservation is flexible, so could cancel and book somewhere else if there is a better hotel. We do want to maximize our time, so willing to pay more for efficiency.

That's my neighborhood in London. (I stay one block away.)

From Heathrow, take the Piccadilly line to Earls Court. Use the Earls Court Road exit. Cross the street directly in front of the station--there is a traffic light--turn right after crossing and walk to the corner which is about 25 feet away. (The street is Earl Court Gardens.) Turn left and walk to the end of the block. The Premier Inn is on the corner.

The tube ride from Heathrow to Earls Court will take about 40 minutes give or take a few. I would estimate you will arrive at your hotel closer to 5:30 than 7:00

DO NOT TAKE THE HEATHROW EXPRESS. IT WILL COST YOU TEN TIMES AS MUCH. AND CONSIDERING YOU WILL HAVE TO CHANGE TO THE TUBE FROM PADDINGTON TO EARLS COURT YOU WILL PROBABLY SAVE NO TIME.

From Earls Court You could take the District line to Westminster and see Westminster Abbey, the Houses of Parliament, Big Ben (covered in scaffolding) and the London Eye.

Or you could take the Piccadilly line to either Piccadilly Circus or Leicester square.

If you are arriving on a weekday please remember it will be rush hour in the late afternnon and the trains will be crowded

I recommend the Heathrow Sheraton, it is next to the airport and the shuttle takes you there. No reason to go into the city.

Depending on what time you get in and what day, there might be a museum open late. For example, the British Museum website says it's open Fridays until 8:30. Lots of ifs: if you have the energy after your flight and if you choose a museum with bag check and check into your hotel after visiting the museum and take Heathrow Express from the airport, you might be able to spend a couple of hours at a museum. Everyone will tell you not to do this after a flight but if it's your only opportunity to see something, it might be barely possible. Late hours are listed in Rick's London book, but be sure to check the museum's website to confirm its hours.

Sounds like you have a great plan, lpk, both in terms of where you will stay and that you won't have large luggage to tote nor have to wait for it at baggage claim.

As for suggestions, that's up to you. Depending on which day of the week, one of the museums could be open late that has great interest to you like any of the Tates, the British Museum or the National Gallery. You could go to the theatre. You could take a boat ride on the Thames. You could show up at a London Walks tour.; no reservations are needed. You might go out for dinner on the town. I suggest doing some research starting at your local library to see what interests you and go from there.

It's easy taking the Piccadilly line back to Heathrow the next morning from Earl's Court. The TFL Plan a Journey website says the ride is 35-40 minutes depending upon the terminal. Just like I would never advise anyone to stay near JFK who has a layover timeframe like yours in NYC, I like your choice of Earl's Court.

Thanks for all the suggestions. I forgot to add - this stopover is on our way home from Europe, back to the US. So our first flight, to London, is only four hours and we don't have to wake up early.

There is a chance we could get on an earlier flight that would get us into Heathrow at 11 am. We'd have to do a same-day flight change, so we'll see how we feel at the end of this trip. The earlier flight would mean getting to the airport at 5-6 am.

When you return to Heathrow be aware that not all Piccadilly line trains go there. Depending on which terminal you are going to the trains should either be Heathrow terminals 1,2,3 and 4 or Heathrow terminals 1,2,3 and 5. For terminals 2 or 3 any Heathrow bound train is fine. For terminals 4 or 5 make sure you get on the right train.

If it doesn't say Heathrow, don't get on the train. Once on the platform, there are electronic signs telling you which train is approaching and how long till its arrival.

Thanks for all the great advice. Now that our trip is a little closer, I'm reconsidering our plans.

After looking at options, we are interested in a river cruise on the Thames. I found one that leaves at 7:30, which I think we can make, However, on another forum someone suggested hopping on the water bus and listening to an audio guide. Any thoughts?

And, reconsidering where we are staying. We are booked at London Kensington (Earl's Court), 11 Knaresborough Place, Kensington
London. I expect that we will head into London, the Thames river cruise or water bus, have dinner (the river cruise would include dinner), and wander around a bit. I want to make the most of our time, so I don't want to stay at a hotel that will add extra travel time. Is it better to stay at hotel convenient to Heathrow or closer to where we want to spend our evening?

Thanks

I regularly stay overnight at Heathrow because I take the day flight from the USA, and fly out about the same time as you are doing the following day ( and vice versa). I sleep at a Heathrow hotel, so I don't have to get up too early in the morning for transport as I'm already there. I'd rather head back to Heathrow at night so I'm ready and there in the morning than in the morning. Personal preference I imagine. My idea of good transport is no scurrying.

FYI: Even though I can, I don't check my bag through Heathrow, because I don't want my bag sitting at Heathrow for 18 hours who.knows.where as that, IMO, is as bad as a too fast connection time between flights for keeping the luggage on track, with me, and arriving as planned. I do check the bag, pick it up at the baggage claim, and walk it to my Heathrow Hotel, and back in the morning. Just something for you to think about. YMMV (I am a person who checks my bags, but can carryon last minute if I want due to the size of my bag.)

Okay now that you’ve changed you plans let’s me throw this option into the mix.
1. Book Premiere Inn at County Hall ( it’s across the Thames from Parliament )
2. Book the Heathrow Express ( way in advance to save $’s) It’s a 15 minute ride into Paddington Station
3. At Paddington Station exit the Express and walk to the Underground station entrance contained with Paddington. Use your credit card and purchase two Oyster Cards from either the manned ticket booth or the Oyster card machines. Put 10 pounds on each.
4. With your Oyster(s) hop on the Bakerloo Line train to Baker Street ( yes, like Sherlock Holmes Baker Street), exit tube and then get another tube train on
The Jubillee Line to Waterloo station. Exit the tube at Waterloo station and then stroll to the Premiere Inn. It’s easy use the London Eye as your focal point as the Premiere Inn County Hall is Right next to it.
5. Check in, freshen up, walk back outside and Cross Westminster Bridge to Parliament Square. Photo ops. Then down the stairs to the Thames where you’ll find Thames Cruises.
6. Take your night cruise. Return to the Westminster Pier.
7. This should give you a few lovely hours of exploration and a goods night sleep.
8. Next day use your Oyster(s) to return to Paddington, and then use your pre booked Express ticket back to Heathrow. Important to know which terminal you are flying from.
9. I’d keep your Oysters as a reminder that you want to return for a longer stay.
10. Great city! You can make the most of you short visit if you plan ahead and prebook!!

Where you are staying is fine for what you plan to do. I almost always stay at Earls Court in a hotel near where you are staying. I’ve also stayed at the PI on Knaresborough Place before and it is usually a good value. It is convenient to Heathrow (under 40 minutes) and it also only takes 15 minutes to get to Westminster on the tube. You should be at the hotel before 6pm assuming your flight lands on time.

I do not think you will be better off staying at Heathrow. While you could choose to stay more centrally, I personally think Earls Court will be fine. Do NOT take the Heathrow Express. It will save you no time if you are heading to Earl’s Court.

Do you have to book the dinner cruise in advance? Having had a number of delayed flights, I’d be hesitant to book anything that requires you to pay upfront.