6 Hr layover at Heathrow

No, not enough time. But you may have time to visit Windsor and it's famous castle. Windsor borders the airport and is easy to reach via Taxi. http://wikitravel.org/en/Windsor_and_Eton

Overseas visitors can only tour Parliament on Saturdays and during the summer openings...the summer openings for Sept is Sept. 1st-3rd and 20th-30th, Mondays and Fridays 9:15am-4:30pm, Tues.,Wed., and Thurs 1:15-4:30pm, Saturdayss 9:15-4:30pm. The tour is 75 minutes long. So if your plane arrives on time...need to plan at least an hour to go thru emigration (it could be less but it could be longer). The tube (subway) would be the cheapest way, it takes 45 minutes, the train takes 30 minutes. Then you would have to either take a taxi or tube to Westminster to the Parliament. So total travel time about an hour and half getting there then back again so it would be close to 2 hrs to 2.5 hrs. 1 hr for emigration, 2.5 hrs travel time (into London and back out), .75 hr tour = 4.25 hours and this could be more. I wouldn't try it myself...you wouldn't want to get delayed and not have enough time to go thru security. There could be a long line at security. If you want a leave the airport I would suggest going into Windsor...it is a 15 minute taxi ride from the airport. You could tour the castle, walk around town a little, have something to eat at a pub and then go back to the airpot.

it takes two or three hours to get where you need to get at heathrow. i got back in march from spain and had not been to heathrow in 10 years. wow, it is large. be sure to eat at gordon ramsay's "plane food." it is awesome, not crazy priced, great service and menu, beautiful view, and fine cocktails. all of heathrow is pretty cool, killing 6 hours at an airport could be alot worse. have fun, be safe.

Thanks to all. We've been to London before and seen Windsor but Parliament was closed. I was skeptical about the possibility but thought I'd check anyway. I would hate to get hung up in the Tube somewhere and miss my ride home.