Nguyen Thanh Trung, 32, from Vietnam, and Capt Mike Green, 74, of Berkshire, who were in the helicopter, died from multiple injuries in the crash near to the tourist attraction in November 2017.
Saavan Mundae, 18, and Jaspal Bahra, 27, both from London, died from head injuries in the accident.
They were both in a two seater Cesna 152 light aircraft.
Both had taken off from Wycombe Air Park, also known as Booker Airfield, about 20 miles away from the crash site.
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At the time of the accident Captain Green, of Long Lane, Newbury, was in the helicopter giving a lesson to Vietnamese military officer Capt Trung.
Mr Bahra, a flight instructor from Tokyngton Avenue, Wembley, was giving a flying lesson to Mr Mundae, a student from Kingwood Court, Richmond.
There was a pre-inquest review in May 2018, but this could not be concluded until the Air Accident Investigation Branch (AAIB) report had been finished.
The proceedings were overseen by Buckinghamshire’s Crispin Giles Butler, senior coroner for the county.
Following the incident, four officers were awarded with Chief Constable’s Commendations for their work.
Thames Valley Police released on their Facebook page the news that PC’s Gray, Burns-Bright and Dudley and Sgt’s Clarke and Perks have all received the Chief Constable’s Commendation for their work at the Waddesdon air crash.
The AAIB are next up to give their testimony in front of jurors.