I've found this PDF document which gives the history of GCA in WW2 and ought to answer your questions better than I can...
http://www.rquirk.com/cdnradar/cor/chapter21.pdf
You'll see that the authors mention that Arthur Clarke was their Radar Technical Officer and worked alongside Luis Alvarez.
One of my school chums had an Aunt who had been a tracker on the trial system...she told me that there was a spot on the front panel which had been marked "Thump here for more gain"!!
In later years, hearing the talkdown controller's voice was an assurance that shortly I'd be comfortably ensconced in the Mess bar....