That's interesting about Melton House. When RfD moved in, each floor was a single open plan office (apart from lavatories of course). It was also allegedly built to have air-conditioning but this was never fitted although the feature of windows not opening (actually, just a little at the bottom) was retained - so the local provider of hired portable air conditioning and a steady income in the summer. Must have been a challenge to make it into individual rooms. Hope the canteen is better than then

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Finally have spoken to my mate who worked there, it was indeed Divisional staff at G.N. House and the staff moved to G.M. York or A.M. Kings Cross as part of 'two-tier'. Sorry, I was sure that two-tier was long before '84. As an aside, he remembers a controller who had moved from Knebworth, wonder where Knebworth Control was geographically. There was also a Motor-rail office there (GN Hse) at the time.