John, in answer to your query there wasn’t anything special about Duxford’s access. This was available to anybody who was within 3 miles of the restricted area boundary and bothered to apply. Duxford did, as a lot of the warbirds and the Classic Wings Tiger Moths don’t have transponders and so an exemption was applied for and obtained. Simples. And now the system has settled down it appears to be working quite well. Hopefully it isn’t so successful that they decide to keep it!!.