I believe the original intention was to have the track doubled slightly further towards Finstock, but that would have meant replacing a low bridge just to the east of where Charlbury Junction was finally positioned.
I heard the same story as IndustryInsider. The original intention was to have a similar length of double track east of Charlbury to that which was provided west of Evesham. This would have allowed trains to depart from Charlbury just before those from the Oxford direction arrive.
Can down trains depart towards the single line at Evesham before one arrives on the up?
I've no hair left, but it would be standing on end, as I don't think that there's another signal beyond Evesham towards the single line which would prevent a down train that had departed from Evesham entering onto the single line at Evesham West Jcn, which would be a bit of a problem if the up train had not cleared that single line.
I'm sure operational flexibility would be greatly improved if the signalling allowed this, but I don't think it's the case.
And wouldn't it be a better use of money east of Charlbury if there was to be a short section of two-tracks and a doubled junction at Wolvercote, rather than a longer stretch of double line extending what's already there at Charlbury? This would allow trains to pass off the Down Banbury line onto the
OWW▸ whilst waiting for an Up train from the Cotswolds to clear, leaving the more important route clear and freeing up things at Oxford station massively.