A decision is due on Thursday afternoon about the future of Abergavenny's 150-year-old cattle market.
The council wants to close and demolish the site so that it can be redeveloped into a superstore and library. Campaigners had hoped an ancient law requiring the town to provide a market would save it. They have now resorted to forcing a judicial review at the London High Court.
The Keep Abergavenny Livestock Market campaign claim that if the cattle market is demolished, "the farming community will lose its centuries-old connection with the town, and the local retail economy will be irreparably damaged."
The council says regardless of the decision work on a new market will begin next week ten miles away near Raglan.