-10 was designed for routes to Africa and the far East for BOAC, allowing a jet to operate out of restricted airfields, hence it's superb performance.
The original 'Standard' version was too closely optimized for BOAC, but the longer 'Super' version had a wider appeal, although originally the 'Super was to be longer still, seating up to 212, DC-8-60 series territory.
However, BOAC had a change of heart, first 3 Standards were cancelled, then 13 Supers. Out of 45 planned, 15 Standards and 30 Supers, BOAC took just 12 and 17 of each respectively.
More 707s were ordered, Vickers had to duped again, in the mod 50's they were building the 707-class V.1000 to a BOAC/RAF requirement, then BOAC decided that long range turboprops like the Britannia were the way to go, so that was the end of the V.1000, then under construction.
Months later, BOAC brought 707-400s.
History repeated in the 60's, many airlines in Africa, the mid and far East and South America were very interested in the VC
-10, but when trade delegations out to sell the VC
-10 arrived at a prospective customer, they found that BOAC had told prospective airlines that they needed a subsidy to operate it, despite BOAC knowing full well by then that the aircraft was extremely popular with passengers, even on the tough competitive North Atlantic routes.
Operating figures were distorted to make the VC
-10 look bad, this an aircraft designed for BOAC!
Limiting sales kept production costs high, which meant that neither BAC/Vickers or the government, were ready to further improve the type, plans for lengthened versions (back to the original 212-seat Super spec.), with improved engines, never happened.
BAC were even designing a double-deck version, seating 264, but with so much negativity on BOAC's part already, it was never going to happen, who would trust them again?
Ironically the VC
-10s that were built went on to be about the most popular aircraft BOAC/BA ever had, with crews and pax, well into the widebody age customers would ask for a VC