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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There were 218 against children last year in Wales but there are growing concerns many more are suffering in silence.
On Monday afternoon, numerous Facebook posts claimed a silver Mini had been stolen from the town with a girl in it.
The silver Mini was found in the River Teifi after a two-hour police search.