Re: Hm...
Are you talking about the Harwell Synchrocyclotron.
"The Harwell Synchrocyclotron was a particle accelerator based at the Atomic Energy Research Establishment campus near Harwell, Oxfordshire. Construction of the accelerator began in 1946[1] and it was completed in 1949".
https://en.wikipedia.org/wiki/Harwell_Synchrocyclotron