Llay Main, Wrexham was initialy sunk to 905 yds No1 shaft
810 yds No2 shaft
Both shafts wound to 776 yds. The Colliery started winding coal in 1921.
After the industry was nationlised in 1947 the shafts where deepend to 1000yds making them the deepest in Wales.
Bold Colliery, St Helens, Lancashire. No1 & No3 shafts where both 1000 yds deep, the deepest in Lancashire.
Clock Face Colliery was only 650 yds deep down to the Wigan series of coal seams the same as its Neighbor Sutton Manor. There is a report that Clock was over 1000yds that is not correct.