Industrial Unrest in the early 1920s

I am researching industrial unrest in the early 1920s, in particular during the economic recession of 1921 and 1922. In the sprimg of 1921, as the coal industry was released from wartime Government regulation, mine-owners imposed swingeing wage cuts on the miners. Any miner who refused to accept the cut was locked out. The miners were set to come out on strike and looked for support to the dockworkers and the railwaymen, fellow members of the 'Triple Alliance' of unions. But, in the 'Black Friday' crisis of Friday, 15 April 1921, the railwaymen and dockworkers announced that they would not support the miners' cause. This effectively ended the Triple Alliance.   According to a report in the Guardian on 12 April 1921 someone claiming to represent staff at Lime Street sent Jimmy Thomas of the NUR a telegram stating that they were refusing to strike. It turned out later that, by his own admission, the unnamed person responsible had in fact left the NUR six months before and only represented non-union labour. But the telegram is nevertheless believed to have played a role in the railwaymen's refusal to support the miners.   I wonder if you know of anyone with knowledge of that period, in particular someone who might know who was the author of this telegram?   Can you offer any guidance on this one?   Kind regards   Andrew Jeffrey. Barnhill Dundee DD5 2QS