Engine failed on motorway wouldn't turn over. Rocker cover off, cam shaft in pieces - No 3 hydraulic cam follower in pieces - cam bearing houses cracked. Thought cam belt failure, took belt cover off belt ok, would have been in tension if the cam shaft was in one piece. No 3 valve still springs up and down returning to correct position. Disc on top of hydraulic cam follower had been broken for a few strokes judging by the marking. So my thoughts are that this broken disc became dislodged and jammed under shaft causing failure. Anyone agree or is it head off?