Mostyn Colliery was a coal mine in Flintshire, North Wales, that was owned in the later part of its operating life by the influential Mostyn family. The colliery was located at Mostyn on the banks of the River Dee. Early history The Welsh writer Thomas Pennant wrote that coal mines at Mostyn were established as far back as 1261, during the reign of Edward I. Records show that in 1294, together with a stone quarry, the colliery had a value of £5 annually, and in 1423 was worth £3 6s 8d. In the early years, coal was transported from the colliery by boats which approached the quay at high water but the changing river course meant that a partial canal was dug to ensure safe passage. Records show that Thomas Cowper and Richard Mason of London leased Mostyn Colliery in 1594. Records suggest that by the 17th century Mostyn was possibly the largest colliery on the western seaboard of Britain and probably the most profitable on the North Wales Coalfield. The Mostyn Family In 1602 Cowper and Mason sold a 13-year lease to Roger Mostyn for £70, beginning the colliery's association with what was to become one of North Wales' most influential families. Mostyn began a programme of expansion, and by 1616 there were three pits on the site. By 1619 the colliery was worth in the region of £700 annually to the Mostyns, which suggests a fairly substantial output. In 1639 Roger Mostyn's successor, Sir Roger Mostyn ordered the sinking of three more deep pits. At around this time, it is noted that almost all coal shipped from Chester was entered into the city records as 'Mostyn coal'. A serious explosion occurred at the colliery in 1673. Sir Roger Mostyn gave an account of an explosion caused by firedamp on 3 February 1675. The explosion "flew to and fro over all the hollows of the work with a great wind and a continued fire, and, as it went, keeping a mighty great roaring noise on all sides". He described how the blast was heard 15 miles (24 km) away, destroyed the winding gear and felled trees. Mostyn also described how the men who were underground at the time of the blast were singed "as if they had been whipped with rods; some, that had least shelter, were carried fifteen or sixteen yards [by the blast] and beaten against the