Wingswinger
2600ft at the top of a loop, if it is accurate, is way too low.
From the AAIB interim report:
The accident flight was recorded by the NATS radar facility at Pease Pottage. The maximum altitude recorded during the final manoeuvre was 2,600 ft amsl (recorded by Heathrow radar), which may not reflect the peak altitude achieved because the radar data was not continuous.