I think Cranwell was a Valiant dispersal. We were there in 1966 for Exercise Unison. We used the 'old' dispersal buildings and on the wall was a box, unplugged, that looked like the standard 'bomber' box connected to the bunker at High Wycombe.
We plugged it in.
It obligingly went 'bleep' and continued to do so every 30 seconds as it sent out its comms security check.