For a number of years, John Bennett and Rob Vernon were involved with the historical study of Welsh metal mining. Their series of seven detailed books on the Gwydyr Forest mines was a substantial contribution to the recording of Welsh mining history. In addition, they were also involved with mine site conservation projects in the Gwydyr Forest and elsewhere in Wales. John sadly died in 2019, and Rob is now involved with other aspects of mining history. At the time of the publication of the first edition of Metal Mines of Llanengan in 2002, it did take their interests further and brought into the public domain a relatively unknown Welsh mining area. The publication of this second edition will hopefully make another generation of mining historians aware of this interesting mining field and is dedicated to John and his wife Elizabeth.