When the VC10K entered service, people were surprised at its lack of AT capability. It seemed daft that it could only 17-18 people in the back of the K2/3.....
It was then explained to us that, had the VC10K been a true AT/AAR aircraft, a number of C1s would have been sacrificed to defence cuts. So by keeping the 'K as a single role supposedly 'North Sea' tanker, 'they' were able to hang on to all the Cs.