Good day, all. We are spending several nights in Paris at the end of a London trip. We will be taking the Eurostar and flying back out of Heathrow. Are we asking for trouble if we leave Paris around 0700 for a flight out of Heathrow at 1425? I'm thinking that with the time difference we'll have approx. 6 hours from arrival at Waterloo to flight departure. Am I correct that we'll then need to transfer to the Picadilly line to tube back out to Heathrow?Any comments?

You will be fine. Most folks on here ask if they can make the LHR/Waterloo connection in 2 or 3 hours in some totally unrealistic time, but you will have plenty of time. you will be at Waterloo a little before 9 a.m.

The trip by tube will be a semi-problem tho' especially if you are schlepping luggage. You will need to walk from Waterloo International across to Waterloo mainline and catch the Northern or Bakerloo line (Northern to Leicester Square, Bakerloo to Piccadilly circus) and transfer to the Piccadilly line.

You can catch a train to Feltham (I think that is the station but other Fodorites may know for sure) and then a bus to LHR.

As Janis says, the train to Feltham and 285 bus to LHR is a better option than the tube, see http://www.swtrains.co.uk/transportlinks/

Just keep in mind the time required before check-in. A year ago I was at Heathrow and if you weren't at check-in 60 minutes before they wouldn't let you to the gate. This happened to us, out connection was too close and we missed out flight to the US.

You should also budget for delays on the Eurostar. Although the train is often on time, just as often it seems to be delayed. Add at least an hour to your scheduled arrival time at Waterloo.

Even with some delay,you should have enough ime for the flight.

You could also take Jubliee Line to Green Park for Picadilly Line.

Looks like we can make it work. Thanks for the help!