Workers in hundreds of the country's biggest post offices have "solidly" supported a fresh strike in a bitter row over jobs, closures and pay.
Members of the Communication Workers Union (CWU) in more than 370 so-called Crown offices walked out for half a day from lunchtime, following a stoppage on Easter Saturday.
The union said the action led to the closure of offices and drastically reduced services and opening times, but the Post Office said over 150 of the affected branches remained open.
The CWU is campaigning against plans to close or franchise more than 70 Crown offices, the larger branches usually sited in high streets, and says staff have not had a pay rise for two years.
Hundreds of jobs would be affected by the Post Office's plans, which would also hit town centres already struggling to attract businesses, the union said, adding that the Crown offices handle around a fifth of Post Office business and 40% of financial services sales.
Picket lines were mounted across the country, and the CWU said the walkout closed offices in areas including Sunderland, South Shields, Redditch, Morriston, Wigan, Wandsworth, Chester-le-Street, Dingle, Hastings, Prestwich, Waterlooville, Aberdeen, Dundee, Bury St Edmunds, Colchester, Norwich, Felixstowe, Dereham, Thetford, Haverhill and Cambridge.
Andy Furey, CWU national official, said on Friday: "Our members have overwhelmingly supported this afternoon's strike action at post offices across the country. They've shown their determination to get their voices heard by Post Office management and will not be brushed off lightly.
"Make no mistake, the feelings of our members are stronger than ever - they deserve fair reward for their efforts and security of employment. Post Office is a successful and crucial public service. We will fight on for fair pay, job security and the defence of this vital and cherished service to communities."
Kevin Gilliland, network and sales director at the Post Office, said: "We will invest £70 million in 300 Crown branches and are proposing to partner 70 branches with suitable retailers. These branches are not closing. Any move to a retailer's premises would offer access to the same range of Post Office products and high levels of customer service in a new modern branch.
"Our pay offer of three cash payments is extremely fair. The CWU's unrealistic demands and threats of further strike action are delaying our people from receiving the first payment of £1,400, which is ready to be paid into their pay packets."