Andy Furey is the National Officer for Communication Workers Union, which represents staff working in Crown Post Offices.
He told ITV News: "A Welsh town like Holywell needs a Crown Post Office. If we lose it, this could be the death knell for the high street in Holywell."
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Videos taken by Aseel Muthana in the months before he left for Syria show he and Kristen Brekke pretending to be on jihad missions.
Decent spells of sunshine expected this afternoon and remaining largely dry. A cold evening with clear skies and showers in the west.
Plaid Cymru, Liberal Democrats and Greens hold informal talks about forming an Assembly election pact but no agreement is reached.