DVTs were to save attaching and detaching locos time, capacity, workload and cost at West Coast destinations. Not for any particular type of loco. The 90s were designed for mixed traffic use which as sectorisation took its hold became less likely for individual locos as a sector would be allocated for each. Hence the first batch being IC, middle batch was Parcels and last the Freight. The locos main aim was to eliminate the 81s/85s and allow some 86s to go East Anglia. Also in 1991 Speedlink freight was abolished so the 90s already had lost some work. If Intercity wanted rid of the 86s and 87s (both still in the heavy maintanence cycles and long term strategies of the time) then many more 90s would have been needed. BR was run on a shoestring and wouldnt have probably ordered the 90s had 81s and 85s been younger and /or East Anglia not been wired....
I still find it strange that such an Intercity outpost like the Anglia mainline become part of Intercity and thus it carried-on using locomotives on such a short mainline. I suppose when planned Norwich and Norfolk were seen as a mostly leisure destination but thanks to high property prices in the South East and "the sparks effect" there was a surge in commuter traffic from Suffolk and Norfolk through the late 80s/90s. I'll have to read Ian Cowley's excellent "Anglia East" book which chronicled the electrification from Colchester to Norwich. Maybe I'll find the reason but you really could make a case for the newly refurbished 309s covering Norwich services, they weren't that much older than the 86s and Mk2s that we had and were perhaps underutilized on the sub-100mph Clacton branch. If East Anglia had been given to Network South East we would surely have seen an AC version of the Class 442 "Flying Pigs" in Norwich. Anyway, sorry, I drifted from Class 90s there.
Don't forget that the Class 93 as part of the Intercity 250 project would have primarily replaced the 87s and some 86s (the ICXC 86 fleet would have been replaced by the 87s or 90s) but John bastard Major's privatisation killed that off.
To be fare all government administrations have never really been pro rail. Apparently the northern powerhouse has been kicked down the road AGAIN!
