Greece's current predicament can be told in numbers, big ones.
The national debt is around 340bn euros.
That is one and a half times the value of everything the country produces, its GDP, or 30,000 euro for every Greek citizen
But even so, Greece continues to borrow, at a rate of more than 20bn euros a year, because of a deficit (the gap between what the Greek government spends and what it brings in from tax revenues) which is running at 10% of GDP every year.
Little wonder then that banks and commercial investors no longer want to lend to Greece. They fear that Greece has borrowed more than it can ever repay and that they would not get their money back.
But if Greece defaults on its debts, that will make its own banks insolvent and do severe damage to banks and financial institutions in Germany, France, the US and elsewhere (not exactly a secret, that).
So just over a year ago Eurozone governments and the International Monetary Fund promised to provide Greece with emergency credit of 110bn euros
It wasn't enough. From 2012-2014, Greece has to find something like 170bn euros or 180bn euros to repay maturing debts and finance the government.
So with what's left over from that original emergency loan, Greece probably needs another 110bn or 120bn euros or so of additional finance (George Papandreou, Greece's premier, put the requirement at 110bn euros over the weekend).
Germany, France and other Eurozone governments don't want to provide all the extra money - which is why they're putting pressure on Greece to contribute about 30bn euros through privatisations and on banks and investment funds to lend 30bn euros or so back to Greece from the cash they receive when existing Greek loans mature.
Goodness only knows whether that 60bn euros from privatisations and so-called private-sector involvement will turn up.
So the potential increased exposure for Eurozone taxpayers of between 50bn euros and 120bn euros is sufficiently large to provide quite a big incentive for the British government to argue that Greece isn't its problem.
Which is why David Cameron, the British prime minister, is insisting that the the UK won't be part of the solution.
Right now, there doesn't seem to be huge pressure from Eurozone governments for the UK to chip in - although the German finance ministry is angling to find a way to hook Britain into the rescue.
The painful truth for Britain is that a Greek default that precipitated big losses on loans to Ireland, Portugal and Spain would be immensely unpleasant for the UK's supersized banks - and, by implication, for British taxpayers too.
And the UK could hardly insulate itself from a Eurozone tipped back into recession, were that to be the consequence of a disorderly Greek default.
In other words, there could be circumstances in which it was in the British national interest to contribute to a Greek rescue (not that you'll hear prime minister or chancellor admit that, in anything other than conditions of a clear and present danger of Greek meltdown).