The class 325s came about as part of the huge “Railnet” project in 1995/96 which modernised the Royal Mail railway operations in partnership with Rail Express Systems (by then part of EWS) and Railtrack. I’ve got a very interesting booklet about the project from 1996 but at 14 pages it’s a bit long to upload here in full. The main aims of Railnet were to introduce distribution of presorted mail in York Containers, which were/are the standard Royal Mail cage trolly, automation and mechanisation to minimise handling, dispensing with loose mailbags except on TPO services and ending the use of ordinary passenger trains to distribute mail. The whole point of the class 325s was to carry York Containers exclusively, no loose bags and no personnel*. There was a lot of invesment - £150 million at 1996 prices - in new dedicated terminals and York handling equipment, new and refurbished rolling stock (including the 16 class 325 units) and it was a 10 year contract running from September 1996 to September 2006. *Although interestingly the 325s do have a PA system, which the original Adtranz Operating Manual suggests should be used to ressassure anyone trapped on board while the train is moving and instruct them not to try to open the roller shutter doors. There isn’t a passcomm but there is a motion detector system which was intended to detect a person on board the train (accidentally or intentionally) after the doors are shut. In practice it is far, far better at detecting wobbling York trollies, which is why almost every class 325 you see moving will have the blue hazard lights illuminated showing that the motion detector system has been triggered.