Their guarantee:
"Backed by HM Treasury
100% secure
National Savings and Investments is backed by HM Treasury, so any money you invest with us is 100% secure."
The Easy Access Savings Account can take up to £2 million per person. In all, depending on your age, NS&I could take more than £6 million per head.
If enough people know about this, and act on it, only Northern Rock will be run-proof. HMG will have to provide an "Irish guarantee". Unless, of course, the Chancellor suddenly welches on government credit, and that really would be the end; or closes the door to new NS&I deposits.
Total retail deposits in the UK are now around £1.17 trillion, of which nearly half is not covered even by the £50,000 deposit protection limit that came into force on October 3rd. So if everybody takes appropriate action, NS&I (and/or Northern Rock) should expect an influx of about £468 billion pounds.
Funds invested in NS&I stood at £84.8bn in 2007/08. A full-scale "flight to safety" would entail an abrupt 550% increase in their deposits.
Get in while you can?
But not into Ireland:
However, experts are already raising questions over the Irish scheme, and asking how much protection it really affords. Adrian Coles, the director general of the Building Societies Association, said savers should write to the Irish Embassy to ask them how they intended to guarantee UK savings, and how they would obtain enough sterling in the event of a bank failing.
"Has the Irish government quantified the potentially huge liabilities it is taking on by guaranteeing sterling deposits in Britain, where household cash savings amount to £1.1 trillion?" he said.
"Savers should beware that, if they switch accounts to take up this guarantee, they are effectively betting on the Irish government's ability to buy sufficient sterling in the foreign exchange markets.