They were also gonna keep some HSTs as Virgin Challengers, but the SRA said no. Seems like the SRA did more harm than good in the early days of franchising, cutting back rolling stock orders that would have provided much-needed capacity, e.g. transpennine express.
If I remember correctly the voyagers were to be ordered in 2 stages, the first part basically as delivered to enable the higher frequency operation Princess and retire the aging class 47s with mk2 carriages.
But the second part the growth was not done due to SRA (or DfT). This would have been lengthening many sets to 6car (even today coach E doesn’t exist). The reason for doing it this way was that if they had been built as 6car, wouldn’t have delivered enough by the proposed timetable change date, and couldn’t operate the old trains under the new timetable.
I am guessing Virgin trains had options to extend the sets at the time of ordering (but can’t find any details) as they probably kept it quiet for commercial reasons), and these subsequently lapsed
What happened 20-25 years ago doesn’t help current problems of crowding, and shamefully there is no decisive plan. Seems to be somewhere between utilise someone else’s cast offs (222s); build some bi-modes; and do nothing. Short term do nothing seems to be winning