Chiltern Line services started running beyond Banbury to Birmingham in 1993, initially every two hours but increasing to hourly in 1994. Until the 168s were ordered and introduced post-privatisation, these services were operated by Class 165s.
Yes, it was a shared service between, the Network South East Chiltern division and The Regional Railways division.
Very occasionaly to start with in May 1993, if they was short of a 165, a 150 would work on the Northern Half of the route covering for a 150, as far as Bicester North, but that was very occasional. Worked by Leamington spa Regional Railways crew.
And passengers had to change trains, from a 150 to a 165 and vice versa in the station.
Soon after in 1994, when it was Hourly, Leamington Spa Guards and Drivers worked to Banbury, and Aylesbury and London Marylebone drivers worked driver only Banbury to London Marleybone.
However throughout from 1993, Banbury to London was Driver only anyway.
Also around 1994, saw through services London Paddington to Stratford upon Avon 165 but Thames division as well.
More notably Sundays was more interesting, because there was two turbo services from London Paddington to Birmingham New Street as a Network South East service.
Giving various traincrew mileage jobs as known to them in the good old British rail days.