Flight Heathrow Airport departs from London Heathrow Airport at 16:35 and arrives at Athens Athens International Airport Eleftherios Venizelos at 22:10.
The flighttime is about 3h 35m. The distance travelled ("as the bird flies"): 3082 Km. So the average speed is roughly 860 Km.
There is an 2 hour time difference between London and Athens