The market test of Britain's credit worthiness
Today is the first serious test of investors' appetite to lend to the British government, since anxieties about the creditworthiness of the British government ratcheted up in mid December.
There's a conventional sale of UK government debt, or gilts, by the Debt Management Office (DMO).
The fund-raising is fairly substantial, £4bn - although less than 2% of all the gilts the DMO has to sell this year.
That said, it is a so-called short-dated gilt, repayable in 2015, which have to date proved easier to sell than gilts of longer maturity.
Perhaps understandably, investors have for some time been keener to lend to the government for five years than for 30 years.
So in a way the more important test of borrowing conditions for the government will be when the DMO tries to sell a gilt repayable in 10 years.
There are of course shades of grey in all of this, in that it has become quite a lot more expensive for the government to borrow this money over just the past six weeks or so.
Based on the market price of this gilt, the Treasury would have paid 2.75% interest for the money in early December, when this maturity of gilt was trading at par. Today it will pay around 3.1% interest, because the price has fallen fairly sharply.
That may not sound like a big change. But if that interest rate increase were replicated across every single pound of the £225bn to be borrowed on markets this year, it would mean the government would be shelling out around £800m extra a year in interest.
And, in fact, most forecasters believe that the rise in what the government will have to pay will be much steeper than that.
Right now I cannot find a banker or analyst who isn't actually or intellectually short of gilts. They all expect gilt prices to fall sharply in the run up to the election, which means of course that the cost of borrowing rises for HMG - which is of course an unpleasant incremental burden for all of us, as taxpayers.
There are those who fear that the interest bill for the government will rise in the coming years by several tens of billions of pounds.
There is of course a more apocalyptic risk - which is that at some point investors lose patience with the government's failure to spell out precisely how it plans to cut public borrowing to more sustainable levels (which I've bored on about in assorted notes) and simply refuse to lend what the government needs.
It is striking that the Greek government, which is rather further down the path to fiscal disaster than the British administration, is employing slightly unconventional means to raise the cash it needs - though is not at the stage of having to request emergency help from other EU members or the International Monetary Fund.
Whatever happens in today's auction, the government would probably be ill-advised to allow market confidence in its commitment to reduce the deficit to continue to drain away.
As has been widely pointed out, the price of gilts would be lower still, if many investors did not believe that there's likely to be a budget-slashing Tory government elected later this year.
Which means that if the popularity of the incumbents were to increase, that could trigger a further fall in sterling and a funding crisis - which would presumably de-rail any gains being made by Labour in the opinion polls.
So the political survival of Labour may well hinge on the credibility of its deficit reduction plans - which is why Peter Mandelson will today attempt to dispel the conspicuous impression of a cabinet divided on the importance of restoring sound public finances.
UPDATE, 10:48: There's no strike of lenders to the government, or buyers of gilt, as yet.
Today's gilts auction went pretty well.
The Debt Management Office sold all the £4bn on offer - and in fact received bids for £10bn, so may increase what's available by another £400m.
But as I said in my earlier note, the Treasury is having to pay a 12% higher interest rate than only a month ago to raise the money.
So it would be wrong to say that conditions for borrowing by the Treasury haven't deteriorated.