Environmental protesters disrupted work at an open-cast coal mine in Wales on Tuesday, chaining themselves to machinery and blockading the entrance to the site.

Miller Argent, which operates the Ffos-y-Fran mine near Merthyr Tydfil, said production was not halted but two protesters were arrested. Others tried to unveil a banner reading “Coal: the black hole in UK climate policy” but were hampered by strong winds.