I'll have a 7 hour layover in Heathrow Airport before connecting to the second leg of my flight. I've read somewhere that it's possible to store your bags at the airport and go on a short tour of the city before heading back. Sounds very reasonable, compared to sitting at the terminal!
My questions are:
1. Has anyone done something like this (I'm mostly concerned about storing my luggage, as well as going through customs again - is that a painful process?)
2. What would you suggest is worth checking out for a short city tour?
I've traveled extensively but have not been to London before.
Thanks in advance!


you'll die of boredom hanging around heathrow for 7 hours, theres nothing to do. you can get a train into town, takes 15mins. your bags will be in transit so you'll only have your hand luggage? even if you took an hour and a half to get through customs and wanted to be back an hour before your flight you could still get to paddington pick up an open top bus whizz around the city and get back in time.

Customs at Heathrow aren't a problem but security is a right pain. Last couple of times I've flown it has been really awful, so leave plenty of time.
The other point is that the train to Paddington is very fast, but it is also extremely expensive.
Once you get to Paddington you have to spend more time getting to the interesting bits of London. Though you may be able to get on one of those hop-on hop-off bus tours there, which is probably a good option for your time frame.
Another option is to go into Windsor/Eton (very close to Heathrow.) The Castle's great, nice high street, nice walks along the river.

There are left luggage facilities at Heathrow.
Here is the cheapest way to see a bit of central London. Buy a one-day zone1-6 travelcard at Heathrow. Take the tube (Piccadilly line) to Hammersmith, walk across the platform, and change to the District line. Take it to Westminster. You'll emerge right across the street from Big Ben and Parliament. Go for a walk. Take the tube back to Heathrow. Allow one hour each way.
Go here to print a tube map and a central London bus map that shows the locatin of major tourist attractions.

Odds are that you luggage will be checked through so you may not have to worry about it and whilst customs generally is not a problem, immigration can be.
Allow at least an hour to get out of the terminal and don't bother with the Heathrow Express as a) it's expensive & b) dumps you in an area of London from which you have to travel further in order to see anything significantly touristy
Instead buy a 1 day Zone 1-6 travelcard and take the Tube to Hammersmith. Then walk 10 feet to the adjacent platform and take a Tube to Westminster. At Westminster leave by the Bridge Street exit and gawp.
Then turn left and go across the river and either go on the London Eye or pass it by whilst enjoying the views. Then walk across the next bridge down river and up to Trafalgar Square. Turn left into Whitehall & see the horses at House Guards then look through the fence at Number 10. Then cut through and decide if you want to visit the Cabinet War Rooms / Churchill Museum. If you do then afterwards return to Westminster and back to Heathrow the same way. If you don't then walk through St James's Park to Buckingham Palace then walk to Victoria Station for a Tube back to Heathrow
This is a useful map of Central London which shows all the sights and where they are
Sometimes the queues at the Underground station ticket machines at Heathrow are long. To save overcrowding, the station staff will tell people to just get on the train and buy a ticket at the other end. If this is the case, make sure that when you change trains go to the ticket office first and get your travel card. It's a regular practice at Heathrow, as long as you get a ticket at the first oppertunity then you get no probs.