The mail online article speaks of plummeting 400 ft.... If this is correct we've all been barking up the wrong tree.
As for now we've assumed the collision took place at around 1.000 ft.
I have no idea where they got their info from.
Ex-British Airways captain killed after mid-air collision with light aircraft causes him to lose control and crash | Mail Online
(and I've never been practically taught an overhead join during my PPL.....(!) taught it myself afterwards and disliked it always.....)