The somewhat forlorn euro has a friend in the Swiss National Bank, an ally that is unlikely to be well pleased by having to play defender. The action gives a neat illustration of not just how euro woes are a problem for the SNB, but in particular how the potential for Greek exit drama is still an important threat to markets.

As investors, and it would seem, most other central banks, sold the euro in December, the SNB stepped up in its defence, intervening to buy the common currency and sell Swiss francs, in the process helping to drive the largest increase in Swiss currency reserves since 2012.

The SNB isn’t doing this to make Mario Draghi feel better, but instead in partial fulfilment of a vow to buy “unlimited quantities” of the single currency to maintain an exchange rate floor of 1.2 francs to the euro it has maintained for more than three years.

By most measures this policy has worked brilliantly, at least in its narrow objective of helping Swiss exporters. But really the SNB has been the beneficiary of Draghi’s “anything it takes” promise, which relieved pressure on the euro in 2012.

As is so often the case, Switzerland’s strengths are also its weaknesses. Since the franc is seen as a safe haven, it has surged in popularity due to Russian economic and political woes and, particularly, as investors took fright at the potential that Greece will elect a government more likely to lead it careening out of the euro.

It does not help that the SNB in setting its exchange floor has written the world a free option to get out of euros and into francs, in whatever size you care to name, at a guaranteed price. That is the kind of policy that works very well until it doesn’t, at which point it is a disaster.

Greek issues aside, the SNB faces pressure because the ECB is fighting its own war against deflation, which calls out for a weaker euro. The SNB, which itself expects deflation in 2015, in December pre-announced that it would impose a negative rate on bank deposits as of January 22, a date that is not coincidentally the next ECB monetary policy meeting.

That move likely was intended to act as a buffer against euro selling and franc buying if, as expected, the ECB introduces new quantitative easing measures. As Eurozone economic data continues to disappoint, this may prove not enough, as it was in December, forcing the SNB once again to buy euros.

This makes the SNB a bit of an instrument of QE for the ECB.

While it likely sells some of the euros it buys for sterling, dollars and yen, a good 45 per cent or so will likely end up in euro-denominated instruments of the various member states. Surely the ECB is thankful for this, but surely also wishes things were otherwise.

For the rest of us, Swiss franc buying is a barometer. “The negative rates from the SNB aren’t working to hold the euro/franc floor even before the ECB QE expectation action on January 22 and this means real trouble for markets. The continuation of flight-to-quality buying matters and it isn’t just linked to oil prices or Greece,” Bob Savage, of Track Research, wrote in a note.

“Even with the cost associated by negative rates for holding Swiss francs, investors in Europe want that safety over the euro. Implication is that we are in for a larger crisis risk should the Greeks leave the euro, oil drop below $40 or the deflation globally get much worse. The knock-on effect for lower rates seems to follow.”

This probably does not end with the Swiss abandoning the floor, but it is important to remember that this is not a frictionless or risk-free policy. More than likely, Greece and Germany work things out and Russian relations improve.

Switzerland protects its manufactures, at a cost, while helping the Eurozone economy.

The Swiss, of course, can print as many francs as they like.

And to the Russians worried about Putin or Belgian dentists fearful of euro break-up they are still a store of value, exchangeable at a guaranteed rate floor for, depending on preference, chocolate or watches.

That is a strength and a weakness.