Mick Martin is the Head of Airfield at Duxford. He asked me to post the following (in italics):

[I]Duxford Air Show Issues.

Whilst I have your attention let me briefly address the issue of the “Fields of Duxford”. CAP 403 makes it very clear that air show organisers and flying display directors have a specific responsibility to ensure that spectators are managed to ensure that they are not under displaying aircraft. To date the CAA have accepted that this responsibility can only be exercised within our own property. However, the issue of offsite spectators is highlighted whenever there is an accident. To watch a show from the fields is an individual decision and the risks are yours to take. That said there are 2 areas at Duxford where I have serious concerns and those are the extended centre lines of the runways. In the event of an engine failure after take off or a loss of power on finals the pilot has only one safe option and that is to land straight ahead. If faced with a field full of people and children the pilot’s only option has been removed and the outcome could well be fatal. I am not trying to stop people enjoying the spectacle free from a safe vantage point but I will continue to try and exclude people from places that endanger the display participants.

Well said.