Hundreds of thousands of teachers, nurses and border guards protesting over pension reform staged Britain's first mass strike for more than 30 years on Wednesday in a confrontation with the government over its austerity measures.
Prime Minister David Cameron played down the impact of the strike, calling it something of a damp squib, saying 40 percent of schools were open and the main London airports were working smoothly.
Unions hit back, saying up to two million public sector workers walked out over reforms that unions say will force them to work longer before they can retire and pay more for pensions that will be worth less.
Union anger has been fuelled by new curbs on public sector pay and hundreds of thousands of additional job cuts outlined on Tuesday when the Conservative-led coalition government cut economic growth forecasts and said its tough austerity programme would last until 2017.
The power of Britain's trade unions was curbed by Margaret Thatcher's Conservative government in the 1980s, but the public sector remains one of their strongholds.
Unions are threatening further strikes next year if the dispute is not resolved but analysts say a repeat of the 1979 Winter of Discontent that helped Thatcher sweep to power is not on the cards.
It's very different to the 1970s and 80s. Many of the services that were run by the public sector have been privatised, said Tony Travers, a public finance expert at London School of Economics.
There is not much evidence that rank and file union members want to go on long-term strikes, he added. The unions have the power to make a fuss and wound but not kill.
BRINK OF RECESSION
Protests, held in towns and cities across Britain, mirror strikes in other European countries where governments are trying to juggle budget deficits with the needs of an ageing population.
Why are the government picking on us in the public sector? asked Kevin Smith, 54, picketing in pale winter sunshine outside parliament in London, where he works as a security officer.
We had no rise the last two years, before that we were getting lower than inflation rises. So how long is it going to last?
Inflation stands at five percent, far outstripping pay rises for public and private sector workers in a squeeze on living standards that is depressing consumer spending.
Retail centres in London and Manchester enjoyed a boost as parents looking after school-age children did some Christmas shopping.
Fears of long delays at London's main Heathrow airport proved unfounded after the government flew home embassy staff to help out and recruited volunteers from other departments to carry out passport checks.
However, underground rail services were not running in Scotland and there were no trains or buses in Northern Ireland.
The government, trying to turn around a debt-laden economy teetering on the brink of recession, says reform is needed as people are living longer and public service pensions are unaffordable.
A coalition of 30 trade unions are taking part in the strike, billed as the biggest walkout since 1979.
Speaking at a rally in the central English city of Birmingham, the leader of Britain's main union umbrella group told Reuters more strikes could follow.
We will have to see, we want to resolve these negotiations by the end of the year, the government's self-imposed deadline, said TUC General Secretary Brendan Barber.
I hope it will be possible to resolve it but if not there is then the prospect of further action including days of this sort, he added.
Sympathy was in short supply from some workers in the private sector. Get back to work and get a maths teacher to give you a lesson. There is no money, said Benedict Crabbe, 38, an investment manager from central England in London on business.
(Additional reporting by Michael Holden and Keith Weir; Editing by Maria Golovnina)