Let me be the first to welcome you to FT!
Just my 2c, I think it might be OK to do this. If you miss one segment of your trip, the airline cancels the rest of your trip. In this case it's OK because JFK-LHR is the last leg of the trip.
Last edited by JetAirways77W; Sep 25, 2014 at 2:40 pm
Reason: bad vocab lol