Employers are licking their wounds after MEPs voted to scrap a key opt-out clause in the Working Time Directive, a move that could change traditional working patterns in the UK for good.
The long-hours working culture in the UK faces its biggest challenge
Within three years, workers may no longer be able to work more than the standard European Union (EU) maximum of 48 hours a week.
Currently people are allowed to opt out if they want to work longer hours, but the EU has been keen to close loopholes in its working rules.
Unions have welcomed the decision to cull hours on grounds of health and safety but many businesses see dark days ahead and warn that more red tape could choke economic growth.
The impact of the new legislation could be felt by thousands of workers.
Working practices at hospitals will be hit as "on call" time by doctors and nurses is classed as regular duty, even when they are not working and fast asleep.
However, the legislation exempts the police, army and emergency services.
WORKING TIME DIRECTIVE
Guarantees workers 11 hours' rest per day and regular breaks
Weekly working time of 48 hours, on average, or less
Minimum annual holiday of four weeks
Night working to be limited, usually, to eight hours out of 24
"Chief executive officers" and "senior managers" also escape.
But other high-earning employees who work long hours, such as stockbrokers, may run into problems.
Similarly, if you are a lawyer and your income is based on bookable hours, then you are bound to work longer hours.
And it is not only the high-flyers that will find themselves caught in a time trap.
Workers who work long hours fall into two very different groups, with high earners at one end of the scale and low earners at the other.
People in the hospitality sector, such as hotel workers, often work beyond the call of duty.
If it ain't broke
UK business leaders are universal in their condemnation of the EU's decision.
"With Europe facing massive economic challenges from China and India, we should be looking to make our labour markets more flexible - not less," says the Institute of Directors.
The current opt-out system works, in large part, extremely well, says Sir Digby Jones at the CBI.
"It gives employees choice in the hours they work, allowing them to generate wealth for their families and companies to generate wealth for the nation.
"People need the opportunity to aspire and earn extra money if they want to."
Pressure group The Forum of Private Businesses agrees: "In the real world, it is necessary for employees to put in long working weeks for peak periods of demand, large orders or deadlines."
A family matter
But unions are cheering the EU's vote. They claim that the opt-out is being abused, and that workers are being forced to work longer than they choose and without extra pay.
"The opt-out is harming the health and safety, the family life and the productivity of British workers," says Tony Woodley, general secretary of the T&G union.
"The UK has the longest working hours of any European Union country."
Labour market thinktank The Work Foundation said removing the opt-out was a step in the right direction and would still leave ample flexibility for employers.
But it said the UK cannot move immediately to a 48-hour limit and businesses and employers need time to adjust.
Even so, would the ruling be enforceable?
Yes, says David Coles, associate director at The Work Foundation.
"If working time rights are not respected, individuals can enforce it in employment tribunals," Mr Coles says. "It comes down to employers and employees generating a change in the culture."
But as one solicitor for Manches law firm points out, enforcement is never as simple as all that.
"Although you can bring claims for unfair dismissal if you're being forced to work over the 48 hours most employees don't do that because they want to keep their job," says Sarah Johnson, partner at Manches.
"It's only when relationships are falling apart that employees use things like the working hours directive as a means of leverage."
"Where the directive has a great role to play is as a protective layer for employees of small businesses," adds Helen Palmer, a worker at JP Morgan.
"When the hours you're made to work affects your ability to have a life away from the office, then I think employees deserve the right to be protected, even if that protection affects the firm's profits."