Chiltern Railways is organising a steam special from Banbury to Bicester North, Princes Risborough and on to the Chinnor & Princes Risborough Railway on Saturday July 3 (actual anniversary is July 1) to mark the 100th anniversary of the opening of the Bicester cut-off - Ashendon Junction to Aynho Junction - which allowed
GWR▸ trains between London and Birmingham to avoid the long haul round via Oxford.
Details are a little sketchy at present, with a kind of watch this space web posting, featuring a picture of the first GWR train leaving Banbury for Bicester in 1910, is here
http://www.chilternrailways.co.uk/news/latest-news/save-the-date-for-the-centenary-steam-express/I'm not entirely sure but think this may be the first train to run through from the main line to the C&
PR▸ line since
BR▸ days, as the connection at Thame Junction has been severed for some time.