From what I can remember from memory of working for Freightliners was that Class 40s were only diagrammed to work the Manchester Trafford Park services to Holyhead as Manchester was the only location in the 1970s/80s to have Class 40 locos available from a home depot (Longsight). I worked at Birmingham Landor Street and the trailing weight for the Holyhead train was just under 900 tons, the diagram was for a Class 47, but, they had Class 40s on the service regularly, until they were all withdrawn by 1984/5, which used to work all the way down from Holyhead as both Bescot and Saltley drivers could work them as well as Chester/Crewe men. Other Freightliner daily services to/from Holyhead over the years were to Southampton, Willesden and Stratford (London), Birmingham and Manchester TP, Class 40s were put on/taken off at Crewe from electric locos that had worked up from the South of England. Services to Holyhead were generally heavily loaded, with traffic to Eire consisting of automotive products, Post Office traffic and a lot of mixed foodstuffs, SmedleyHP, Lockwoods, Crosse and Blackwell and Heinz all had factory outlets in Southern Ireland in those days and tinned foodstuffs are a heavy commodity in bulk. When I worked at Nottingham FLT we had weekly containers of Irish Peat in 20ft and 30ft boxes for delivery to various farms/garden centres in the East of England, that was another heavy commodity.
Cheerz. Steve.