Signs beside the A149 near the police station and Fat Birds bike shop warned it would be closed for road works from tomorrow.
But there was some confusion this morning, after drivers found the road closed a day earlier than the signs said.
A Norfolk County Council spokesman said: The sign is wrong. The letters and public info notice all say the 13th.
'We are sorry for the error and hope that it has not caused any additional inconvenience.for anyone expecting the road to still be open today.'
A crossing to the park is being improved, by repairs to the central island. Diversions have been signposted.
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