I can't believe ANYONE might know this ….

I often talk aeroplanes with my 85 year-old Dad,though he doesn’t share my love of flying-boats.
He frequently tells me that you were only lucky enough to see a flying-boat if you lived near the coast.
Growing up in Croydon,Dad saw lots of different aeroplanes at Croydon Airport,but he didn’t see a flying-boat until 1938 when one took part in the flypast at the opening ceremony at Gatwick airport.

My question is : what flying-boat could it have been ?

Was anyone reading this actually there ?