It is a T6 Harvard. They make a hell of a prop noise and I could never understand why it didn't have a bigger or 3 or 4 bladed one. The noise apparently is from the prop tips going through the speed of sound .
They had one as chase at A&AEE Boscombe Down for years and it used to drive my mother up the wall whith the noise! But they chose to live close to the airfield..
the Navy called them SNJs up until 1962. it IS a North American T-6 though. the Army Air Corp called them AT-6 and after the USAF became its own service they were just T-6.
in the States theyre known as Texans, the models exported to the British Commonwealth nations call them Harvards