Leicester1, I was 500 m from the aircraft when it began to go wrong. I don't believe he was trying a barrel roll, but a climbing, steeply banked right turn. What I saw was consistent with losing the flow over one or both wings. When I saw the first 'twitch'. I thought he was intending to roll. This bothered me because the speed and height seemed insufficient. Then it went over, the nose dropped, and the rest you know. My wife believed he rolled the aircraft away from the M11 and the road where all the villagers stood, and aimed towards the empty field. This was not the first fatal I have seen, and believe me, I always hope they will be the last. Our condolences to families and friends.