Hundreds of Crown Post Office managers will go on strike today in a row over pay.
Unite warned that the action will hit services at the larger branches, usually sited on high streets.
The union, which represents 900 managers, said its members have not received a pay rise since June 2011 and accused the Post Office of "dragging its feet."
More top news
Lottie and her dog Marley confronted a man who had taken a laptop and goods from a Lush store in Oxford.
Feeling colder with a biting, bitter windchill
A thoughtful teenager has taken Valentine's romance to a whole new level by buying 900 flowers and giving one to every girl in his school.