After passing this on the way home from Cambridge, I could not pass up the urge to have a quick look. After getting caked in mud going the long way around and then feeling stupid after finding an extremely simple way in, it was a good find. Most of the outbuildings were locked but you can easily see what is inside through the windows. Light was diminishing fairly quickly so I had to be quick.
History
Mullard Radio Astronomy Observatory is home to a number of large aperture synthesis radio telescopes, including the One-Mile Telescope, 5-km Ryle Telescope, and the Arcminute Microkelvin Imager. Radio interferometry started in the mid-1940s on the outskirts of Cambridge, but with funding from the Science Research Council and a donation of £100,000 from Mullard Limited, construction of the Mullard Radio Astronomy Observatory commenced at Lord's Bridge, a few kilometres to the west of Cambridge and was opened by Sir Edward Victor Appleton on 25 July 1957. This group is now known as the Cavendish Astrophysics Group. (Wikipedia)
Pictures
Full set available here.
Full set available here.
Thanks for looking.