[G6Tanuki]

In the early-1980s one of my clients used quite a few GEC4080 computers, and I spent some time at their production-facility in Elstree Way, Borehamwood. The original 4080 took up several 5-foot-high 19-inch equipment-racks; however at the same site they had developed the 4080M version - not much bigger than a shoebox - that was to be part of the Nimrod AEW aircraft's electronics.
We were shown the 4080M and were truly amazed, both at its small size and - when we were told it - the cost!
[Alas the 4080M was not up to the task and was a significant part in the decades-late delivery/final cancellation of the entire Nimrod project].

I'm sure that sustained effort could have developed low-power Nuvistor-type valves - it's worth remembering that even in the early-1950s there were subminiature wire-ended valves using 0.625V heaters consuming a mere 20 Milliamps and 22.5V HT. There was also the multiple-valves-in-one-envelope 'Compactron' range - which were not all that small but showed an interesting though obviously-doomed direction. Desk calculators [the ANITA range] used cold-cathode thyratrons for digital logic in the early-'sixties. Also the German 1920s "Loewe' multiple-valve-elements-and-associated-resistors-and-capacitors-in-one envelope technology is worth remembering: part of me wonders if it wouldn't have been possible to combine these technologies to produce a 'single-valve' equivalent of basic circuit-elements like flip-flops, dividers, counters, op-amps etc just as we did a decade later with the first ICs?