David Prosser: An unlikely windfall from the financial crisis?

Whisper it quietly, touch some wood and cross your fingers, but British taxpayers may yet come to view the worst financial crisis since the Great Depression as a nice little earner. It looks increasingly likely that all the billions pumped into our deadbeat banking sector will eventually come back to us – with some profit thrown in.

Last summer, ratings agency Fitch said the total long-term cost to taxpayers of supporting the UK financial sector might be £40bn. As the outlook improved, Gordon Brown was, by the end of the year, claiming the taxpayer would "make a profit from what it has done". Others were sceptical, but it looks as if the Prime Minister may eventually be proved right.

Let's be clear. Such forecasts assume the Bank of England's £185bn special liquidity scheme for the banking sector, due to be withdrawn at the end of 2011, does not incur losses. Few expect it to. Similarly, the chances of losses on the £125bn or so of bank debt guaranteed under the Government's Credit Guarantee Scheme are thought to be very low. Should that change, so would the bill.

That leaves direct intervention in the banks. The first liability is the £27.5bn the taxpayer has paid out in compensation to savers of banks that have gone under.

Most of this will be refunded, via the wind-up of the defunct banks and from levies paid by the financial services industry. Small losses are possible – and getting money back from Iceland is proving harder than expected – but Fitch's best guess is a deficit of £300m.

What of the asset protection scheme, in which the Government has pledged to cover 90 per cent of losses on £280bn of Royal Bank of Scotland's toxic assets? Well, remember there is an excess: RBS has to pay the first £60bn of losses. On that basis, estimates when it joined the APS in November were that the eventual taxpayer bill might be £2bn after fees.

In addition, let's assume £2.5bn of losses (the compensation, and the expectation that Northern Rock won't be privatised at a profit). Everything, then, depends on the taxpayer's stakes in RBS and Lloyds, respectively 84 per cent and 41 per cent. Both positions remain in the red – the break-even price for RBS is 50.5p (it was trading at 44.0p last night) and 122.6p at Lloyds (which closed at 60.1p). But both banks have now reported improving trading in the past month. It may be possible to cash out profitably enough to cover losses elsewhere within the lifetime of the next Parliament.