Dai Evans
Dai Evans was a miner who worked at the Llanfairfach Colliery. Following the mysterious death of Ted Hughes, Evans insisted on venturing down into the mine alone to find out what killed him, over the objections of Dave Griffiths and Bert Pritchard. He soon did discover what had killed Hughes, when he himself contracted the "green death" after either coming into contact with the toxic waste being pumped into the mine by Global Chemicals, or was attacked and bitten by a giant maggot.
He managed to call Dave on the phone down in the mine before collapsing. Bert, along with Jo Grant from UNIT, went down into the mine in an effort to rescue him, but due to Hinks sabotaging the lift, they became trapped underground with the ailing Evans. While the three were awaiting rescue, Evans grew sicker and sicker and eventually died from the disease he'd contracted. His body was found by the Doctor later when he and Dave managed to get the lift repaired and came down into the mine themselves.