The BBC was to announce the axing of 2600 jobs overnight - one in nine of the total staff - risking a wave of industrial action over what is the biggest round of job cuts in the organisation's history.
Most of the cuts will come in BBC newsrooms, from which hundreds of journalists will be laid off, and in departments making documentaries.
Mark Thompson, the BBC director general, who has been criticised for not negotiating a more favourable licence fee settlement from the Government, will also take the knife to the corporation's output of drama, children's programmes and its services in Scotland and Wales. Radio Five Live and the rolling news channel News 24 will also be hard hit.
Unions are already drawing up battle lines, describing the programme of job losses as "unprecedented" and describing morale at the BBC as being at "an all time-low".
The BBC Trust, which oversees the corporation, gave its approval yesterday to Thompson's six-year strategy, entitled Delivering Creative Future, which is intended to create a more streamlined organisation for the digital age beyond the switch-off of the analogue signal in 2012 and place a greater emphasis on internet-based services.
Sir Michael Lyons, the trust's chairman, said: "We are confident that the plans we have approved today will safeguard the core values of the BBC at a time of radical and accelerating change in technology, markets and audience expectations."
Senior BBC sources tried to play down the scale of the blood-letting yesterday, saying that the net loss would be 1780 posts, after programmes of re-skilling and the creation of new jobs.
But BBC staff are likely to react with anger to the announcements. Gerry Morrissey, assistant general secretary of the broadcasting union Bectu, said he expected the BBC management to be put on notice of impending strike action, after a meeting of the main unions, which is likely to trigger a strike ballot. Staff could be on the picket lines by late next month.
The cuts to the corporation's main newsrooms will be deepest of all, totalling more than 360 lost posts, some 12 per cent of the total staff of BBC News.
After protests from presenters such as Jeremy Paxman and John Humphrys, the BBC's flagship news programmes, such as Radio 4's Today, The World At One and BBC2's Newsnight, have been largely safeguarded. One source said: "We've sought to protect the big beasts like Today and Newsnight.
"They're not exempt but they have been largely protected and it's the daily newsroom, the 24-hour machine, where we have looked to drive out the duplication."
In looking for cuts, BBC management is looking to reduce duplication, with specialist correspondents being expected to work for all BBC platforms - website, television and radio - much more than is currently the case.
News 24, which has already incorporated the major bulletins into its schedule to reduce its own output, will be obliged to cut some of its weekend talk-shows and programmes.
Factual programming, which includes documentaries and educational programming, will lose several hundred jobs because of "an over-capacity" of production staff in London.
Morrissey said he was concerned at reports from employees that letters with offers of redundancy had already been prepared for named members of staff before talks had taken place between management and unions. "Morale at the BBC is even lower than when John Birt was director general," he said.
WHY IS THE BEEB CUTTING JOBS, AND HOW WILL THE UPHEAVAL AFFECT ITS OUTPUT?
Why are we asking this now?
The Director-General of the BBC, Mark Thompson, will announce the biggest round of staff cuts in the history of the Corporation. It is expected that at least 2600 posts will be axed over the coming five years. Allowing for natural wastage, the creation of new jobs, and some rehiring, that makes a net loss of 1780 jobs.
Most of those who are sacked will go fairly quickly, within the next 18 months.
The news and documentary programmes will take the biggest hits. The news team alone is likely to lose 300-400 jobs. Thompson also claims that there are more people than necessary employed on "factual" programmes, particularly in the light of plans to move work out of London and to commission more programmes from independent companies.
Why is this happening?
This is the outcome of talks the BBC had with the Government a year ago over the cost of a television licence.
Thompson tried playing hard-ball during the talks, telling the Government rather publicly of the dire consequences if they held down the price of a licence. He even threatened that if he did not get the money that he wanted, he would abandon a multimillion-pound plan to open a new centre in Salford, northwest England, where 1500 staff from sport, 5 Live, children's programmes and the internet operations were to be redeployed.
Prime Minister Gordon Brown, who was then Chancellor of the Exchequer, refused to budge. The BBC was presented with a six-year deal under which the licence will increase from £131.50 ($357) to £151.50 by 2012, not enough even to keep up with inflation. The Salford project will go ahead anyway. Thompson is now looking for other ways to fill a £2 billion black hole in its finances.
Which staff should the BBC go without?
There are any number of people inside and outside the Corporation willing to air their opinions about where the axe should fall, if fall it must.
Norman Fowler, a former journalist and Conservative chairman who now chairs the Lords committee on communications, said yesterday that, if he had to choose, he would rather the BBC made one drastic cut, like closing down BBC 3, rather than spread the misery everywhere.
But BBC 3 is one of the Corporation's most effective vehicles for reaching young viewers, who watch less television than their elders because of the competing pull of the web and computer games. One in five 16- to 34-year-olds watch BBC 3.
Fowler particularly did not think news broadcasts should be cut, an opinion vociferously shared by some of the BBC's best known employees. Jeff Randall, until recently the BBC's business editor, has said that the BBC has legions of meeting-obsessed, decision-averse middle managers it could do very well without.
It will be the middle managers who decided whose jobs must go, and they will doubtless think of themselves as indispensable.
Is the BBC's reputation at risk?
The BBC has had a bad year, convulsed by controversies ranging from the misrepresentation of the Queen - an episode that led to the resignation of the Controller of BBC1 earlier this month - and phone-in deceptions.
In addition, it faces never-ending complaints of political bias. These come mostly from people who claim there is a left-liberal cult in the corporation, but also from the left.
The BBC's coverage of the Israel-Lebanon conflict last year also drew 5000 complaints, some from people who thought they were pro-Hizbollah, others from people who thought they were pro-Israel. But these problems reflect the very high expectations from the BBC.
What about the BBC outside Britain?
The BBC's reputation outside Britain can be gauged from the fact they made £101 million profit last year selling home-made programmes overseas, and that 233 million people around the world listened to or watched the World Service. That is one arm of the BBC with nothing to fear, because its money comes from a separate budget, direct from the Government.
While the rest of the corporation faces cuts, the World Service has been told it can expand its operations, especially in the Middle East.
What does the BBC cost to run?
Last year, the BBC spent £3.3 billion and it directly employs more than 23,000 staff. Thousands more on the outside look to the corporation as their main source of income. This makes it an important regional employer, and a major source of income for anyone involved in the creative industries.
About a third of the total budget is spent outside the BBC, commissioning programmes from independent companies, buying in programmes, or paying freelance artists. Just over a quarter of the BBC's budget, £864 million last year, was spent outside London.
What about the big stars and their salaries?
The people at the top of the BBC are well paid by almost anyone's standards. Thompson received £788,000 in pay, expenses and pension contributions last year.
The BBC's highest paid performer, Jonathan Ross, has a deal worth £18 million over three years. Graham Norton has a contract worth £5 million, and Terry Wogan is paid £800,000 a year. None of the big earners is likely to be affected.