The Local Government Act of 1972 saw the boundary between Oxfordshire and Berkshire changed with many local areas being moved from Berkshire into Oxfordshire. Prior to this change the County of Berkshire actually extended almost into the City of Oxford. The Boundary change resulted in the main line between Oxford to Didcot and from Didcot to Uffington, together with the Abingdon and Faringdon branch lines, all once in Berkshire move to Oxfordshire.
This talk by Laurance Walters covers the above lines and branches that were once in Berkshire.
Non-members are welcome, but a small charge of £3.00 is payable to defray costs such as tea and biscuits.