trains stopped apart. Driver fatigue was found to be the cause of the SPAD. Operations Chiltern Railways The 165/0 units were originally delivered in Network SouthEast livery for used on routes including fast services from London Marylebone to Princes Risborough and Banbury and local services from Aylesbury to London and Princes Risborough. In this role they replaced the DMUs. They were later used further afield, when Chiltern services were extended to serve Leamington Spa, Warwick, Solihull and Birmingham Snow Hill / Birmingham Moor Street railway station. In December 1993, due to a downturn in traffic as a result of the recession, units 165001-007 were transferred from the Chiltern lines of Network SouthEast to the Thames lines (from Aylesbury to Reading depots). All vehicles had their tripcock equipment removed before transfer. The following year, unit 165007 was returned to the Chiltern lines, followed by 165006 in 1995. Due to unavailability of tripcock equipment upon their return, the units were coupled cab-to-cab and operated for some months between the vehicles of other units as semi-permanently formed four-car units - until tripcock equipment became available, allowing them to be restored to operational two-car units. Following privatisation, two former Chiltern units (165003 and 165005) were repainted into Thames Trains livery. Chiltern Railways inherited 34 Class 165/0 units from Network SouthEast, and the remaining five were returned from Thames Trains in 2004 - leaving Chiltern Railways operating the whole subclass. After privatisation they continued to work similar services as before but, with the arrival of the faster Class 168 Clubman units, the 165 Turbo trains were displaced and are now found less often on expresses to Birmingham, generally working on shorter routes such as stopping services to Aylesbury, High Wycombe, and Stratford-upon-Avon and also the Birmingham Moor Street - Leamington Spa local services. A new depot was built at Aylesbury in 1990/1991 for the maintenance of these trains and has been enlarged since British Rail days, with the addition of a wheel lathe. Light maintenance and refuelling is carried out at Wembley LMD and Tyseley TMD, and units can occasionally be found at Stourbridge LMD. Units are also regularly stabled in the Marylebone station environs, Aylesbury South Sidings and at Banbury, where a further depot is currently under construction at the south end of the station on the western side of the line. All Chiltern units were refurbished between late 2003 and early 2005. Air