It was Ken Dineen's .30 SC powered one off scratch built bike. 4 pictures of it at the bottom of the NITRO page http://www.skiptonclub.net/nitro.htm
Now it has an OS engine and is noticeably quicker and sounds far better. Lapping at almost Superbike speeds in the hands of World Champ Colin McCabe, it's just awesome to watch. The latest nitro race video from Sunday shows a little of it in action on the (rather slippy) track.

John