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
World Number 4 Murray has won their previous five encounters, but Karlovic tops the tournament's aces leaderboard so far.
The Britain's Got Talent judge was accused of singing the national anthem in an American accent and getting the words wrong.
Greece's controversial Finance Minister Yanis Varoufakis has released a defiant statement of resignation entitled 'Minister no more!'