In Britain, unlike most other countries, mine owners did not own the coal that they mined. It was owned by landlords who received a royalty payment according to how much of their coal was mined. To understand the extent to which this separation between the ownership of the mines and the ownership of the coal was a barrier to the development of the coal industry in Britain during the inter-war period, it is necessary to have a detailed picture of the pattern of royalty ownership. The 1938 Coal Act nationalised the ownership of coal and for several years during the early 1940s, ten Regional Valuation Boards met to value the coal owners' claims for compensation. By 1946, over 26,000 claims by 13,000 different owners had been met. The valuations of each claim is recorded in the minutes of the Regional Valuation Boards, and it was this information that was used to build up a picture of the pattern of royalty ownership. Variables Colliery 'area', registration number, claimants' name and the valuation of the claim.