There is another 'master and slave' on the ingot train -still coupled cab to cab. I asked if anyone knew a definitive date as to when were they turned round and Vic Smith replied: 'Extracted from Barrow Hil Roundhouse Archives Improvements for this problem happened in 1966/67 when the master units were turned and the cab positioned at the furthest end from the hump. The jumper cables also had to be re-routed and this work was carried out by Doncaster works with D4501 done in October 1966, D4502 by the end of November 1966 and D4500 in January 1967. Thanks Vic