To the OP (Lucky 284):
I was in London 8 months ago and I could see only 1 monument per 1/2 a day.
So choose one which you would like to go and see and come back. No point in seeing many places. It would take you one hour to clear the customs (depending on the line) and 1 hour to even think of reaching the place you want to go. You have to be back before 1 hour at the gate and the return journey can take you 1 hour. So it leaves you with 2 hoours at the max. at your disposal. Remember that you can get lost very easi8ly in the big city and not make it back in time for the airport.
I would recommend the following :
Option 1 :
1. Westminsiter abbey (seeing from outside)
2. Parliment (seeing from outside)
3. London eye

Option 2 :
Buckingham palace (seeing from outside)

Option 3 :
Tower bridge (walking through it)
Thames river (seeing from Tower bridge)
A famous place near the Tower bridge (built by Henry)- See from outside
London municipality building (seeing from outside)

All the best of catching the flight

Peace by TK

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I am a Gents and not a Ladies.

Thanks everybody for sparing your valuable time. I really appreciate that. To be very precise ,we are reaching terminal 5 at 7am and leaving terminal 5 for toronto at 1530 hrs. If anybody can suggest any 4 to 6 hour sight seeing tour operator, I shall be obliged. I am unable to take any decision with so many suggestions available and very less time available with us.

Tk is right, Heathrow is huge and downtown is quite a drive (1 hr to be approximate) taxis are hell expensive a one way trip can cost you Pound 60 above, buses/subways can take longer and you need to know exactly where to catch them and what to do. If you are single you can attempt it, with a family its not impossible but hard. If you can find any tours from your terminal which can bring you back on time...go ahead. Without a tour London hopping is not easy if you are there for the first time. Airports are far away from main tourist area. I'm assuming your luggage is in transit and you don't need to bring it out and check in again.

Hope it helps....................Jona

Option 1 per TK is good .... if you have spare time after that ... visit Trafalgar Square and walk around a little bit before taking the Tube back to Heathrow .....

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Fido.

Thanks Bhai log for all your guidance. I have decided to get down at 3 subway/tube stations viz Tower Hill, Charing Cross and Westminster . I will be buying day pass for this trip. Here goes the final plan now. Need your approval for the plan below( FYI I am arriving heathrow at 7am)

1 Take Piccadilly line at 8am (direction Cockfosters) from terminal 5 heathrow
2 Change at Gloucester Road to the District line (direction Upminster).
3 Leave the train at Tower Hill. Spend 30 minutes there
4 At Tower Hill subway take the District line (direction Richmond).
5 Change at Embankment to the Bakerloo line (direction Harrow & Wealdstone).
6 Leave the train at Charing Cross. See trafalgar square. spend only 30 minutes.
7 At Charing Cross subway take the Northern line (direction Morden).
8 Change at Embankment to the Circle line (direction Clockwise).
9 Leave the train at Westminster. spend 2 hours
10 Around 1pm ,At Westminster subway take the District line (direction Richmond).
11 Change at Gloucester Road to the Piccadilly line (direction Heathrow Terminal 5).
12 Leave the train at Heathrow Terminal 5. My flight from terminal 5 is at 1535 hrs to toronto


Need your approval please for this plan

Are Guru aap to great nikale ....

I don't remember the Train directions but the plan looks good .... If you can take out spend an hour at Trafalgar Square and walk towards Covent Garden ... only if time permits .... 2 hours shd be good enough for Parliament Square /Big Ben / Westminister Abbey ... 10 Downing is also close by ...... London Eye ... and Thames all in the same vicinity... keep sightseeing flexible ... I would have done it in the reverse though ... reach Westminister first , and then Trafalgar and Tower Hill ... But I understand there could be route limitations .

Good Luck. Keep your own eating provisions handy .... we carried a thermos for tea also ..

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Fido.