East Midlands
I was an ATCA at East Midlands when it opened in April 1965. One Sunday during that summer British Midland sent all 3 of their Argonauts to an event over in Lincolnshire (50 years and 2 strokes have erased the memory of exactly where) to operate pleasure trips.
They all came back together; the duty ATCO, it might have been Harry Pollack, opened the window and said "now you know what a squadron of Spitfires sounded like".
I had previously flown on G-ALHS Luton/Jersey/Luton the previous summer for a jolly; the customs officer letting us take in the full DF allowance although we'd only been out of the country for about 3 hours.
I recall that 'HG and 'HS were 2 of the 3 aircraft but I can't remember which was the 3rd.