The Kent Coalfield was a coalfield in the eastern part of the English county of Kent. The Coalfields Trust defines the Kent Coalfield as the wards of Barham Downs and Marshside in the Canterbury district, and the wards of Aylesham, Eastry, Eythorne & Shepherdswell, Middle Deal & Sholden, Mill Hill and North Deal in the Dover district. Coal was discovered in the area in 1890 while borings for an early Channel Tunnel project were taking place; the resultant Shakespeare colliery lasted until 1915. In 1911, investigation into whether there was other workable coal was planned. Six 'bore holes' were put down in search of coal (at Rushbourne, Hoads Wood in Sturry, Herne Bay, Reculver, Chitty (which is near Chislet) and Chislet Park near the future site of Hersden). In the early years many collieries were sunk but were short-lived and the East Kent Light Railway was built to exploit the anticipated business. Extensive plans had been drawn up by 1914 for major coal exploitation in east Kent, and the coalfield expanded rapidly in the late 1920s and early 1930s, with its maximum output reached in 1936. The outbreak of war and disappointing test results resulted in four collieries surviving: Betteshanger, Chislet, Snowdown and Tilmanstone. Had coal been more easily accessible, the open, rural landscape of east Kent could have changed beyond recognition. Geology Various geologists, including Robert Godwin-Austen, theorised that the geological conditions in East Kent were conducive to the existence of coal and therefore the potential for coal mining. Godwin-Austen put forward his views in 1857, and they were accepted by Sir Joseph Prestwich, who was a member of the Royal Coal Commission from 1866 to 1871. The rock sequences found in the "concealed coalfields", all those of the counties of Kent, Berkshire and Oxfordshire have been formally renamed in recent years using terms established for the South Wales Coalfield. Much of the strata now assigned to the Warwickshire Group was formerly assigned to the Upper Coal Measures.<ref>Waters, C.N. et al. 2007. Lithostratigraphical framework for Carboniferous successions of Great Britain (Onshore). British Geological Survey Research Report, RR/07/01 60pp</ref> The following seams are recognised. They are listed in stratigraphical order with the uppermost/youngest at the top and the lowermost/oldest at the bottom: Warwickshire Group Kent № 1 (Beresford) seam Kent № 2 Kent № 3 Kent № 4 Kent № 5 Kent № 6 (Millyard) seam (South Wales) Upper Coal