Q&A: What does the Greek debt crisis mean for the UK?
While the Greek debt crisis occupies world leaders at the G20 summit of the biggest economic powers, should we fear the potential fallout here?
What effect will the Greek referendum have on the UK?
The prospect of a referendum on the second Greek bailout deal has increased uncertainty that Greece can deal with its debts, and has again led to widespread falls across global markets.
In the City, the FTSE opened 2.2% lower after the referendum announcement.
The referendum call also ensured Greece dominated the G20 agenda.
Meanwhile, even if the European situation is resolved, the National Institute for Economic and Social Research says the likelihood of the UK falling back into recession is 50% - rising to 70% if European leaders continue to "muddle through".
What will be the UK contribution to any bailout fund?
The prime minister has distanced himself politically from any bailout of Greece - despite announcing the UK is considering giving more cash to the International Monetary Fund.
With one eye on Eurosceptic MPs in his own ranks, he remains adamant that the UK will not contribute to any bailout fund for the euro.
But, arriving for the G20 summit in Cannes, he also said it was "right" for Britain to consider boosting the funds of the IMF.
That could mean eurozone nations like Greece are indirectly helped by the UK.
The UK currently provides £29bn ($46bn) of the IMF's £600bn ($950bn) lending capacity.
About £4.9bn of UK money is held in the IMF's fund but it could draw down up to £29.4bn from the Treasury in certain circumstances.
How much does Greece owe us?
UK exposure to Greek debt is relatively small. According to figures from the Bank for International Settlements, UK banks hold $3.4bn (£2.1) worth of Greek sovereign debt, compared with banks in Germany, which hold $22.6bn (£14.1), and France, which hold $15bn (£9.3).
When you add in other forms of Greek debt, such as lending to private banks, those figures rise to $14.6bn (£9.1) for the UK, $34bn (£21.2) for Germany and $56.7bn (£35.4) for France.
What will it mean for the UK if Greece leaves the euro and defaults?
If Greece leaves the euro, a default is inevitable.
David Buik, of the brokers BGC Partners, says there would be "horrible connotations" if Greece left at this point.
While we still do not know exactly how much Greece owes the banks, he suggests a figure of 490bn euros. If the debt is not repaid, "that has terrible effects on the banks; it makes recapitalisation incredibly difficult", he says.
UK banks are linked to the other European banks through the sale of insurance and other guarantees on debt default. A new "credit crunch", meaning less money available for banks to lend to businesses and individuals, would have a direct impact on UK manufacturing, UK exports and overall economic activity in the country, leading to a lower GDP growth.
Reduced economic growth would mean that the government also had less money to spend on the services that it provides.
"Frankly, it means we're heading nose-first straight into recession", says Mr Buik.
Another big concern from the UK perspective is that it would trigger a chain reaction, as the other "peripheral" eurozone economies - Portugal, Spain, Ireland and Italy - would find it impossible to service their own debts. Fathom Consulting estimated in the early summer that UK exposure to these countries is around €70bn (£60.2bn).
What about UK trade with Europe?
More than 50% of the total UK trade is done with the EU and the UK enjoys the benefits of the European single market. As part of the measures to stop the eurozone crisis, the eurozone leaders are likely to move towards an even closer co-operation on economic issues for their 17 countries.
That could potentially undermine the single market that all the EU members, regardless of whether they use the euro as their currency or not, benefit from.
This is why David Cameron insisted on being part of the summit on 26 October, despite French President Nicolas Sarkozy's opposition - to safeguard against measures that could, in the future, lead to protectionism within the eurozone, to the detriment of those EU countries which are not part of it.
It is not possible to quantify how much UK/EU trade will be lost if the EU does not come up with a solution to the crisis, but less money in Europe would certainly mean less trade between the UK and its most important trading partner.
What would the collapse of the euro mean for the UK?
A Europe entirely without a euro is unlikely, so it would all depend on which countries would leave the currency - and therefore the extent of UK banks' exposure to their debt.
Any country leaving the euro would have to replace it with some sort of currency, and this would take time - during which there are likely to be banking casualties.
Politically, a collapse of the euro would be a massive boon to Eurosceptics who are a growing influence within the Conservative Party.
The collapse of the euro would also increase pressure for treaty changes within the EU, allowing David Cameron to call for EU powers to be repatriated to Britain but also re-opening demands for a referendum on the UK's membership.
What is the UK hoping to achieve at the G20 and what is its influence?
Before the Greek crisis overshadowed the event David Cameron had a two-fold ambition for the Cannes summit: to demand swift action to resolve the debt problems of the eurozone and to encourage growth in all G20 countries.
As Britain is not in the euro, the prime minister's influence on eurozone meetings has been limited.
But at the G20 he will be joined by other more powerful countries - the US, India and most importantly China - which also want the problems of the eurozone resolved.
In September the prime minister joined five other G20 countries in calling for coordinated action from the world's leading nations to stimulate economic growth.
The six leaders were insisting an agreement should be reached at the Cannes summit. That now looks unlikely.