Same sort of problem as the Trident, Dougloid.
The VC10 project started as an RAF 'expressions of interest' invitation for a military jet trooper/transport aircraft. The RAF naturally wanted 'short-field' capability. The transport project got to the prototype stage but was cancelled in a round of defence cuts.
Menawhile, though, Vickers had been talking to BOAC ('British Overseas Aircraft Corporation' - basically the government again) about a civil version. BOAC did the same thing with the VC10 as BEA did with the Trident, placed a small order and then set to work largely to ruin the design with one 'special requirement' after another.
In particular, their pre-occupation at the time was with the 'Empire routes' - which included South Africa. Those were 'bus stop' routes at the time, and stops on the way to Cape Town included Rome, Beirut, Cairo, and then a number of 'hot and high' airports all the way down through Africa. Almost unbelievably, they ALSO said that they didn't see much future in transatlantic services.....
So the VC10 finished up with a lot of power, but also a big wing area and an unbelievably-massive array of flaps and airbrakes. All of which cost performance, especially range.
True to form, when BOAC finally got the small numbers of VC10s they'd ordered, they found themselves having to rush it into service on the fast-expanding North Atlantic trade - for which, of course, thanks to them, it was pretty ill-suited. And beyond THAT, of course - you've guessed it!
- they began imploring the government to let them buy 707s........
"Once you have flown, you will walk the earth with your eyes turned skywards.." - Leonardo da Vinci