Sorry, the Comet beat it by two weeks.
Avro Canada C-102 Jetliner:
The first flight of this four jet aircraft occurred at Malton Airport, Hamilton, Ontario, Canada, on 10 August 1949.
Comet:
First engine test runs of prototype G-5-1 were made on 2nd April 1949 with roll out on 25th July after a complex program of engine tests. Two days (27th July) later the Comet made it's historic maiden flight which lasted 31 minutes. Crew: piloted by de Havilland Chief Test Pilot John Cunningham, John Wilson as co-pilot and the flight test observer was Tony Fairbrother.