Many thanks for this informative link Nutty

It confirms that Bert was helped in his mining song collecting by The National Coal Board around 1950. In practical terms songs were "sent" to Bert by working miners.

Two of these songs Blackleg Miner and Banks of the Dee were among the first half dozen songs that I learned around 1963-4.The more I sing them the more that I am convinced that they were not conceived much before 1950

In a similar vein Gresford Disaster was "collected" in Sheffield and again repeated singing since 1966 confirms my gut reaction as to the origin of the song.

They are still wonderful songs and none the less worthy of being sung!!