The 12 UK banks and building societies downgraded by Moody’s on Friday are no dirty dozen. The rating change does not signal a problem with them. It merely acknowledges the government’s reduced support for UK lenders post-crisis. The Treasury, Financial Services Authority and Bank of England have said that banks cannot now assume automatic taxpayer support in a crisis.

But Moody’s downgrades coincided with a rerun of the European Banking Authority’s stress tests of the region’s banks. The fear is that proper market-based writedowns of their sovereign debt holdings could lead to a European Union-imposed recapitalisation of weak banks. That prompted a sell-off in the shares of UK banks – including Barclays, which was not downgraded.

Yet the banks are mostly well capitalised and have not been swept up by the same negative sentiment as their eurozone counterparts. They still fund themselves relatively easily and their exposures are manageable. At the time of the EBA’s stress tests in July, the total net direct sovereign exposure of Royal Bank of Scotland amounted to 12 per cent of core tier one equity, Berenberg Bank estimates. RBS has since halved its Greek exposure, so that could be 100 basis points less by now. At Lloyds Banking Group the comparable ratio is 0.2 per cent. Barclays’ exposure is 22 per cent using the same measure as it has a bank in Spain. But this risk is already amply reflected in all the banks’ valuations – and will remain so for as long as the eurozone sovereign debt crisis rages.