Thanks for asking
justapax it was BA LHR-JFK. I was able to get one of the discounted seats, in the run-up to the closing of the service. They had 1,000 seats that were Westbound and return via 777. The other 1,000 seats for the Eastbound, were only sold to Americans.
The day after my arrival, I was on a New Jersey beach with friends and we saw the fabulous machine on a clear afternoon. Which was the same as the previous day.