By Torin Douglas
BBC media correspondent
Five months ago, when he took over as the BBC's director general, Mark Thompson said the media world was moving so fast that the BBC would have to change more radically than at any time in its history.
Mark Thompson says more of the licence fee will go to programmes
At the time, that remark received less attention than it deserved, both within the BBC and outside. Now we know he meant it.
The scale of the changes announced today is not easy to comprehend.
Take the job cuts. The BBC's headline figure for redundancies is "an initial 2,900" over three years - a figure echoed by the trade unions in their responses.
But some media reports have talked about 5,000 jobs and more.
Who is right? It all depends what timescale you are looking at.
Of those 2,900 redundancies, 2,500 are in backroom areas or "professional services", such as personnel, finance, property, legal affairs, marketing and public relations.
Forty-seven per cent of jobs in those areas will go, either as redundancies or in "outsourcing" of the roles.
The other 400 jobs will go from the "factual and learning" programme division - but that is only the first tranche of programme-making jobs that will be lost.
Programme areas now face efficiency cuts of 15%, under the BBC's "value for money" review, followed by further job losses as more productions are outsourced to independent producers.
Next Spring, more details of these job cuts will be revealed, including some in news and current affairs.
On top of those, 1,800 jobs are expected to come off the BBC books when two of its commercial subsidiaries, BBC Broadcast and BBC Resources, are sold off or outsourced, in another of the day's announcements.
That helps to explain the figure of 5,000 jobs.
The fact is that no-one can accurately predict the full impact that the Thompson strategy will have on jobs.
It depends on how much of the BBC's production ends up in the hands of independent producers, and it will also be affected by the fact that the BBC is ploughing the savings straight back into more programme-making.
Explaining this, Thomson uses journalism as the example: "It's true that we will be asking existing programmes to look for efficiencies. But the total amount of money we spend on journalism will go up - not down. The same is true for radio, television and new media."
So this is a very uncertain time for BBC staff, and likely to remain so for many months.
Adding to the uncertainty is the unprecedented move of people, resources and channels to Manchester.
Eighteen hundred jobs will switch from London when BBC Sport, 5 Live, children's TV and radio, New Media and a large slice of education programming move to the BBC's new state-of-the-art broadcasting centre in the city.
There are fears that the combination of redundancies, independent productions and the move to Manchester could leave the BBC with empty offices and studios in London, just as it has completed several new buildings there.
But these are long-term plans and much will change during the BBC's next charter.
It will take five years for the Manchester centre to open and, as Thompson has demonstrated, even five months is a long time in broadcasting.