A pub in Pontlottyn was given the Hollywood treatment when Michael Sheen joined a meeting of United Valleys Action Group.
The Newport-born actor, 45, played Tony Blair in The Queen and starred as David Frost in the dramatisation of the Frost-Nixon interviews.
He joined the group at the Blast Furnace Inn as part of the filming of a BBC Wales documentary about the Chartist uprising of 1839 when workers demanding male suffrage marched to Newport, only for 20 of them to be slaughtered by British soldiers.
Mr Sheen was interested in the group’s views on democracy and social change, on the 175th anniversary of the Chartist movement.
The organisation has been active in local campaigns in the Heads of the Valleys for over three years and is currently campaigning against the proposed Nant Llesg opencast mine near Rhymney.
Chris Austin, Secretary of the United Valleys Action Group, has previously criticised Caerphilly councillors for a lack of support to those opposed to the mine.
Mr Austin said: “Michael spoke really well – he was on the money. He’s quite switched on politically.
“We were saying how we cannot get a voice and he is looking at the Chartists and democracy so he drew the parallel. He said what you think is that democracy is failing you.
“Someone else taking an interest in what you are saying gives you a lift. It was very exciting.”
United Valleys Action Group has applied to the Welsh Government to have the planning application called in, meaning Welsh ministers could decide whether or not the mine will go ahead.
Mr Austin said: “We want the planning decision called in because we have got a lot of cross party support in the Assembly itself but at the council we are stuffed.
“The largest group is the Labour Party and they won’t even talk to us. We’re doomed if it gets decided by Caerphilly County Borough Council.”
A Caerphilly County Borough Council spokesperson said: “We are aware that the group has approached the Welsh Government asking for the application to be called in.
“However, we have not heard anything formal from Welsh Government. In the meantime we will continue to consider the application and report it to our Planning Committee.”
Caerphilly Observer understands the decision to proceed with the mine could hinge on the survival of Aberthaw Power Station, as this would be the main customer in Wales for coal extracted from the Nant Llesg surface mine.