Without a doubt that was the Daily Express Airshow at the old Gatwick Airport, which was a grass commercial airfield at that time. There were 2 events 1948 & 49 and I attended both. My parents took me to the first and they paid 10 shillings each for my sister and I to fly around the circuit for 10 minutes in an Air Enterprise De Havilland Dragon Rapide 8 seater biplane. There was a Taylor Airocar there for sure. There is still one left flying today and it appeared at the Reno Air Races a few years ago. The original Beehive round air terminal was opened in 1936 and still exists today as a museum. I worked in this building in 1953 for Trainsair, a charter airline using DC-3s and Avro Ansons.