The thing I find really strange about this tragic accident is the aircraft’s track (Figure 1 in the report). The pilot tracked roughly south and ended up significantly east of Chalgrove and then for unknown reasons, turned left and not right.
The report mentions that there was a GPS on board and the Nav radio was tuned to the Daventry VOR. Turweston is very close to the radial that would allow a direct track to Chalgrove. It seems very odd that apparently neither of the available navigation devices was used.