The Class 309 was different from many of the other electric multiple units built during the same era, as their design was closer to a standard Mk1 passenger coach than to the commuter focussed designs of the previous Class 302, 307 and 308 units. Initially they were to be introduced on the East Coast Main Line, with the modifications to the roof of Kings Cross station proving to be too expensive however electrification of the ECML was paused. This created a fleet of 24 units without a use before they were even completed. Eventually however it was decided the fleet would operate on the newly electrified London Liverpool Street to Clacton route, with the units being given the name ‘Clacton Express’. Clacton Express units remained limited to few routes on the Great Eastern, thanks to their design being unsuitable for the more commuter focussed routes closer to London. Eventually however the units would see use as far as Ipswich and Harwich, when both routes was electrified during 1975.

Many of the Mk1 derived electric multiple units in operation on the Great Eastern Main Line, including the Class 302, 307, 308 and 309, saw replacement in the form of the Class 321 electric multiple unit of 1988. A few of these units would see further use with Regional Railways, with Class 309s seeing further use in the Manchester area as far as Crewe and Stoke-on-Trent, as well as Manchester Airport when the station opened in 1996. Following passenger use a pair of units (renumbered 960101 & 960102) saw use by Railtrack testing the newly fitted ETCS on the Old Dalby test track.

Two complete units remain in preservation, with both units preserved following the conclusion of ETCS testing work during the mid 2000s concluded, 960101, now returned to 309616, is preserved in its full 3 car formation at the Tanat Valley Railway. 960102, now partially returned to 309624, is preserved by the Clacton Express Preservation Society in various locations, BDTC 76965 and MBS 61928 are at the East Anglian Railway Museum, while DTS 75962 is at the Rushden, Higham and Wellingborough Railway.

(1) TCS White and Blue 61928 (Ex 960102) at the East Anglian Railway Museum. (2) Network SouthEast 76965 (Ex 309624) at the East Anglian Railway Museum. (3) Network SouthEast 78037 and 71205 (Ex 312792) at Castle Hedingham on the Colne Valley Railway.  (4) Class 309 standard class interior. (5) BR Blue 78037 and 71205 (Ex 312792) at Castle Hedingham on the Colne Valley Railway. 

Additonal information on the Class 309 'Clacton Express'

Gensheet - Class 309 history

https://www.gensheet.co.uk/class309.htm

Clacton Express Preservation Group

https://www.clactonexpresspreservationgroup.com/

Motion History: Class 309 - The Clacton Express

https://www.youtube.com/watch?v=kFPUuPemTCM