With fears that Spain's banks may need to be bailed out, Channel 4 News looks at the state of the banking sector in Britain.
Although the Spanish government has attempted to dampen speculation that it will request an immediate bailout from the EU to shore up its banks, many believe it will have to do so in the future.
During the 2008-09 financial crisis, RBS and Lloyds had to be bailed out by the British taxpayer. Since then, they and other British banks have made efforts to strengthen their "capital buffers" to withstand future shocks.
They have done this by increasing the amount of money available from shareholders that can be called on if other sources of funding are under strain.
Under international rules, all banks currently have to ringfence 4 per cent of their balance sheet to deal with a crisis. In Britain, mindful of recent history, they have gone further, typically ringfencing 10-11 per cent.
According to Britain's banks, they are well capitalised in comparison with financial institutions in the eurozone. The British Bankers' Association says the amount of money held for emergencies has risen from 7.6 to "almost 12 per cent" of total balance sheets in the last three years.
But even if they are in fitter financial shape than European banks, would British banks be able to cope with a Greek exit from the euro and/or Spanish banking implosion?
I don't think it is reasonable to say that anyone knows for certain. The key is what policy decisions are made by euro area governments to resolve this. Michael Symonds, Daiwa
PIRC, which carries out research for institutional investors, has produced figures which suggest Britain's biggest banks are already preparing to write off a further £40bn in bad debts, with RBS and HSBC hit the hardest.
But RBS told Channel 4 News: "We don't recognise the numbers quoted by PIRC. Our capital, liquidity, and funding positions are strong and we comply fully with IFRS international accounting standards."
Events in the eurozone are intertwined with concerns over bad debts.
The Bank of England and the Financial Services Authority, which regulates the banks, have been working together to ensure banks are well capitalised, while the banks have been reducing their exposure to the eurozone and carrying out stress tests to see how they would cope if Greece leaves the euro.
RBS has reduced its exposure in Greece, Spain, Italy, Portugal and Ireland and no longer lends money to the Greek government, although it is owed £0.8bn by Greek companies. In Spain, it maintains "strong relationships" with banks and companies, but it will not comment on individual firms.
Along with Lloyds, it is a big lender to Ireland, which has already received a bailout, while Barclays has more exposure than Britain's other banks in Spain and Italy.
RBS's post-crisis strategy has been to shrink its balance sheet so it is no longer "too big to fail", playing a smaller role globally and concentrating more heavily on Britain.
According to figures from the Bank for International Settlements from Dec 2011, British banks' exposure to Greece is small, but their business in Spain and Italy is much bigger, particularly their lending to the private sector.
British banks have loaned $10.6bn to Greece: $1.8bn to the government, $1bn to banks, and $7.8bn to the private sector.
In Spain, a total of $83bn has been loaned: $4.4bn to the government, $12.9bn to banks, and $65.8bn to the private sector.
In Italy, the total figure is $59.4bn: $8.4bn to the govt, $6.9bn to banks, and $44bn to the private sector.
Michael Symonds, an analyst at Japanese investment bank Daiwa, told Channel 4 News that British banks had increased their firepower in recent years and their direct exposure to eurozone banks was "manageable".
'The great unknown'
But he said "the great unknown" was might happen if there was a "disorderly" Greek exit from the euro, with knock-on effects in other European countries that could affect British banks' loans to eurozone companies as well as banks.
Mr Symonds said: "I don't think it is reasonable to say that anyone knows for certain. The key is what policy decisions are made by euro area governments to resolve this."
There was a danger that access to private funding could dry up, which would mean the Bank of England stepping in, he said.
In short, while British banks' loans to eurozone banks look manageable on paper, if eurozone companies default on their debts - a very big if, admittedly - British banks could end up paying a very big price.