The test of Halifax were conducted in early 1943 by a Polish test pilot Stanisław Riess. He did a series of flights to find the reason of structural failures of Halifaxes, and on his last test, on 4 February 1943, the aircraft disintegrated in the air, with the loss of Riess and crew. As far as I have read, the problem was in the wrong ballance of the rudder, which caused uncontrollable falling leaf, and in the effect structural failure of the tail.
I am always feeling cold, when I realise that the man just went for suicidal mission.