First comments on Serve. What were they popping when they doodled 3-fuselages...some schemes are comic-book, as impractical as those 10-engine VTOLs. UK designers 1950/60s were not expected to be able to spell Maintainability, Reliability - that was for erks, but really...
So...why did they waste their time. Did they have nothing better to do?
Well...no.
No writer has picked up this point:
UK Aero was, is, military-driven for the same reason Billy the Kid robbed banks: that's where the money is. So they employed hefty Design Offices/Experimental Depts., believed R&D to be a business end-in-itself, and resisted licences-IN, all because their prime Buyer, MoS/MoA, put Independence above Interdependence. So he was willing to accept the Military element of a DO into overhead in calculating contract prices.
In 50/60s most production contracts were priced after an early batch had been built cost-plus, so actuals were known. The Men from the Ministry then simply arrived at a learning curve that reduced unit direct labour content (man-hours) over quantity, so £X p.m.hr, x Y m.hrs., then put overhead on that number (some learning was also applied to material scrap rates). The overhead rate (X% - some 00s) on direct labour m.hr was to include that proportion of the cost of the DO that had UK military potential. That is why I babble that PV was rare-to-non-existent in UK Aero.
MoS did not argue against the existence of a DO (indeed it was a qualification to Tender), nor against its size - a matter for Owners. They tried to exclude costs irrelevant to Ministers: DO effort wholly civil. But they did not dismiss comic-book schemes, because innovation is what a DO is for. So: make-work doodles, hoarding skilled labour waiting for the next Big Thing, would be a cost-for-Owners if the scheme was manifestly civil, but (partly, even muchly) for MoS if it could be linked to something which might interest RAF Director of Operational Reqts.