Although I'm not sure if they are commemorating the first flight at RAF Cranwell, Jet Age Museum, Gloucester commemorated the unofficial first flight, last month.
For those that don't know, during high speed taxi trials at Glosters' Brockworth factory, the E28/39 hopped into the air for a short time. The aircraft was then transported to RAF Cranwell for her "first" flight.
Ian Whittle came along and buried a time capsule at the museum, on the edge of Gloucestershire (Staverton) Airport.