Ahh, bit of t'internet trawling and a plausable answer has been found i think...
http://www.safespeed.org.uk/forum/viewtopic.php?f=5&t=21832&st=0&sk=t&sd=a&start=80
About 7th post down
Seems its an upgrade to an analouge camera thats been converted to digital
Well done Steve, knew you'd find it :smthumbup
And to quote that post, here's the answer:
"FREEDOM OF INFORMATION ACT 2000 - INFORMATION REQUEST
Your request for information has now been considered. The information you have requested is enclosed below:
Thank you for your email concerning the new equipment at the existing camera sites at xxxxxx
The sites referred to have been recently converted from old wet film technology cameras to new digital technology cameras, as part of this process a new flash unit was installed at each of the sites to allow more illumination at the site and therefore give a better clarity of photo.
The aerial on top of the flash unit is used to transmit the photos taken by the camera to the police headquarters computer server. It is primarily used to send data however it is possible for the camera to receive data when needed by the police server. The aerial dose not interact with the radar unit contained within the camera housing"