New 6 part series from 4th September on BBC Wales, so most of us will have to use iPlayer (clip from chartists cave): https://www.bbc.co.uk/programmes/m000m93p
First one is the caves episode (Gower, Chartists & DyO):
https://www.bbc.co.uk/iplayer/episode/m000m93p/hidden-wales-with-will-millard-series-2-episode-1