Do you know about the proportion of HST vs 165/166 back over the years? I am curious about it.
In Thames Trains days,
everything on the Cotswold Line was a Turbo (165/166) apart from two return journeys operated by Great Western with HSTs.
In the morning, the first GW HST arrived at Paddington around 08.30, another (the Cathedrals Express) 09.40. In the evening, they left Paddington 17.10 and (Cathedrals Express) 18.30. (There was nominally one off-peak GW service, but this was subbed out to Thames Trains to operate with a Turbo, I think from 2000 or so onwards.)
When FGW took over the Thames area (first as FGW Link, then in the expanded Greater Western franchise) most Turbos were replaced by Adelantes (180s). In due course FGW relinquished the Adelantes, with HSTs and some Turbos replacing them on Cotswold duties - though the balance tipped in favour of Turbos after a few years.
Move on a few years and FGW got five Adelantes back, which meant most Cotswold services could be covered by Intercity-standard stock. Not all, though - there were still a handful of Turbo duties, including the odd Moreton-in-Marsh terminator, and one horrible Sunday working from Paddington to Hereford and back. Turbos still made regular appearances when the Adelantes had self-combusted or HSTs were required elsewhere on the network.
Now, of course, the line is all-IET apart from the daily up/down "Halts" train that stops at the tiny Oxfordshire stations. It's rare to see a Turbo depping for an IET, but not unheard of.
People forget Oxford - Malvern is a very slow trundle along mostly single track railway. It's a glorified branch line in effect.
Nope. It's only single track from Wolvercot to Charlbury and from Pershore to Norton Junction, certainly not "mostly". Numerous sections have 90mph-100mph linespeed.