Suggestions for 1 day London Excursion

You won't have nearly the amount of time that it looks like you do. Remember, you have to allow at least two hours (preferably more) before your ongoing flight to get through security when you come back to the airport. And with the delays that Heathrow has been experiencing lately getting through passport control on arrival, you won't be ready to head into the city anywhere near 1:30 (perhaps 3:00). Others can suggest specific train possibilities, but I would suggest that you limit your visit to Windsor, which is a short taxi ride away from Heathrow.

You'll have a good 5 hours. Hopefully, you won't have baggage but if you do: http://www.heathrowairport.com/heathrow-airport-guide/services-and-facilities/left-baggage Cough up the dough and take the 15 minute Heathrow Express into London. From Paddington Station which is where you will arrive take the tube (District or Circle line) from to Westminster Station. Mind The Gap and follow signage to Exit 1. Climb the fews stairs. Before you is the Thames, the London Eye and Westminster Bridge. Turn to you right and look up. Start your few hour tour of London there!

IF you land on time it will probably be 2:00 (maybe later) before you get in line for immigration. Some flights at Heathrow have to park at 'remote' gates and deplane onto buses to get to the terminal- this can add time getting to immigration. Under good conditions (few other flights landing at same time, no labor problems with immigration staff, no Olymipc 'slow down', etc.) you can anticipate 30 min. to an hour waiting in line. Could be more- or less. If you have to store checked luggage you loose even more time. That means you are looking at being ready to head into London (or to Windsor) around 3:00-3:30 at best. The tube will be cheapest-will take about an hour to get to central London. The Heathrow Express (most expensive) or the Heathrow Connect (second most expensive) trains will take 15-30 min. (not inculding wait time) and will take you to Paddington Station. From there you can take the tube- another 15-30 min. under good conditions to get to where ever you decide to site see. In other words- It will be 4:00-6:00 before you get to see Big Ben (most likely). If you have an international flight you will need to be back at Heathrow NO LATER than 7:20- and that is not giving you any time to spare for long check in and security lines. That means you would need to be back on the tube no later than 6:15 or on the Connect by 6:45 or the Express by 7:00. You get anywehre from 2 hours to only 15 min. to see things. And that assumes that there are no delays on the tube (common- especially on weekends) or the trains (not as common). To me it is not worth it to risk missing your next flight. There are lots of things to do at Heathrow- resting, shopping (many, many, many shops), taking a shower and getting a snack in one of the airline lounges, getting a meal at one of the many restaurants, etc.

Having done just this recently (my layover was 10 hours), the hard part right now will be immigration. If the line moves well - you're good. If the line moves slow...you may get out of one security line to get back in another. Assuming your flight lands on time and immigration isnt completely bonkers, that means you have from 1500-1900 to play with. The expedient way into town is with the Heathrow Express. To and from Paddington in about 15 minutes. Just bear in mind that you'll want to be at Paddington for your return trip by 1900.

And then there are my friends who had a similar layover in Rome a few years ago. They decided to chance it. Everything was going fine until he slipped in a puddle of coffee in St. Peter's (I know - totally random!) and, being a biggish guy, managed to break his ankle with the force of his fall. Needless to say, they missed the flight home. Just sayin'. I'm a pretty fearless person, and love last-minute adventures - but I tend never to mess with flights. Given what could go wrong - traffic jams, one of you gets separated from the others, etc., etc. - I'd stay at the airport.

I agree totally with Kira. It may be a phobia, but for me the flight connection is always my first priority. I don't believe in pushing my luck; if there is something I really want to do, I will plan a future trip around it. I would pay a little more to avoid having an 8-hour layover in the first place. Since you are already trapped into that timeframe, aim for Big Ben and Westminster Abbey, spend no more than two hours in the heart of London and start back to Heathrow when you still have at least four hours to spare. Hopefully, if your kids are better at time managagement than mine were, that accounts for teenagers' tendency to wander off.