Herald was a 1956-turbine variant of Miles 1947 M.73; 48 were sold cf.786 F-27: in ’95 a ’71-built F-27 was bought for $1.2Mn. by Channel Express/Hurn to replace its last Herald whose price new in 1963 had been less. Aer Lingus (then a BEAC-Associate) had been Launch Customer for F-27 in 1956, discarding HP's bid, unimpressed by weight of Victors in work, underwhelmed by HP’s priority on the richer product. They sought performance guarantees, fixed prices/specs/delivery, including spares and tools: Greek to HP. At that point no-one knew the practical operational issues posted here.
It was quite difficult actually to buy a Herald: R.Jordanian A.F. took 2, R.Malaysian A.F.10 as HP knew his way around military business (though 3/62 MoA chose 31 HS780 as RAF Andover C.1). But airlines were alien: HP Ltd. had ventured beyond Dover to terra incognita only twice - 1919 to China for 6 bombers-as-transports, and SABENA,Belgium, 1922, 2(+13 licenced) others. HP preferred to sell in Whitehall’s one-stop shop to RAF and Imperial A/W. Civilians despaired and went to Fokker, who cared. Flight Intnl. 23/12/98 Herald obituary: “the pilot feels he is exercising some skill if he taxies (smoothly...cockpit: ) tolerably comfortable for relatively short flights” but its virtue had been seen as “pleasant handling characteristics...pilot appeal.” Airliners are not sold to pilots.
Failure was not Govt.'s fault. HP was given Launch Aid by way of imposition on BEAC of an order for 3, funded from the Scottish Highlands & Islands budget (today: EU cohesion fund). Netherlands Govt. did not order 12 for RNethAF until the type had penetrated wide civil market..inc. Oz, to HP's chagrin. I suggest brick dunny, normal Brit heaviness, over-engineered, heedless of operating economics, which in UK then were never a Design Case.