So after 4 1/2 years, I am finally headed back to the US (Los Angeles) in 4 weeks. In order to secure a great rate, I accepted a flight with a 10 hour layover in London.
Anyone got suggestions of relatively inexpensive, interesting things to do in that time frame? I figure between customs and pre-check in times, I probably have around 6-7 hours to kill.
When I had a layover not quite as long as yours, I took the tube to Picadilly Circus, I think the station was. Walked over to Buckingham palace in time to get a good spot for the changing of the guards. I know it’s a tourist cliche, but I’d wanted to see it in person every since I saw it on Captain Kangaroo. Just walking around Westminster was pretty cool. If was too late to get tickets to see the Abbey, but it’s right there if you get there early enough or arrange tickets in advance.
One thing I forgot to mention is that I have been to London before and scoured all the really touristy places, so those are low on the priority list. Sorry **zagloba **- thanks for the suggestions 
I think the point still remains - from Heathrow you’re about an hour out of the centre of London by Tube, so anything you’d be interested in doing there is probably within reach - the Transport for London Journey Plannermay be useful for you. So you might just want to wander around Soho, book shops around Charing Cross Road, check out Borough Market (depending on your timing) etc etc - depends on what you’re interested in.
It is quite easy to take the Tube to Kew Gardens. It’s not a whole day thing, but it is very doable in that amount of time.
Is the OP changing airlines on their itinerary? Because Heathrow is BIG and you might need to account for a lot of walking if you have to change terminals.
But 6 hours still sounds about right, so I’ll echo the others. I had about that long in my London layover when I came back from Austria last year, so I bought a Time Out in the airport and looked it over for any special events or temporary museum exhibits worth checking out while I was on the Tube (it is about an hour, so that’s plenty of time to research before you have to decide what stop to get off of). We just walked around Leicester Square, had an Indian lunch buffet, and explored some shops before heading back. Pretty casual, but if you want to hit the ground running, you’ve got enough time to get some good exploring in before heading back.
Just be sure whatever carry-on you have with you is something you won’t mind lugging around.
Call me cynical, but my lack of faith in Heathrow, airlines and the London underground all lumped together would make me wary of straying too far. Not that you want to hang out at the airport.
I’ve always been happy just wandering around the Tate Modern (which only requires one line switch, but I’d still time it).