text: Following successful trials of the initial locomotives, a production run of 43 locomotives were ordered as part of the Bournemouth Electrification and built by English Electric at their Vulcan Foundry between 1965 and 1967. They were initially classified as Class JB and numbered E6007-E6049. They differed slightly from the six earlier machines, most notably having an increased tractive effort as well as a higher maximum speed (90 mph as opposed to 80). Following the introduction of TOPS, they became Class 73/1 and were renumbered 73101-73142. One locomotive, E6027, had already been withdrawn following accident damage and so was not renumbered. Further changes were the use of large round Oleo buffers with a pneumatic withdrawal mechanism rather than the traditional coach style (oval) saddle buffer which relied on a pin and spring mechanism. As the JA examples came in for overhaul over the years, the saddle buffers were also replaced making visual identification of the differing machines almost impossible from a distance.
  From new, all members of the class were fitted with the Pullman style rubbing plate between the buffers allowing them to close couple with Southern Region electro-pneumatically controlled electric multiple units and diesel electric multiple units for push-pull train operation – the reason for retractable buffers.
  Being built to the Hastings Line gauge, the locomotives were able to be used on all routes of BR's Southern Region network.
  Technical details
  The design parameter of the Class 73 was to provide a secondary main line electric locomotive to the then Southern Regions "mixed traffic" requirements, with the added ability to deliver, shunt and collect freight to and from yards adjoining the electrified network under diesel power. The shunting requirement meant these locomotives had dual controls on both sides of the cab.