In Syria, the Quds and the IRGC have been fighting to bolster Bashar al-Assad’s depleted forces since at least 2012, while the Saudis and the other Gulf monarchies have lent assistance to the various Sunni rebel groups fighting to destabilize the government in Damascus.

In Yemen, Iran-backed Houthi militiamen drove President Abd Rabbuh Mansur Hadi from the country last year, prompting Riyadh to intervene in order to prevent Tehran from establishing what would amount to an Iranian colony on the kingdom’s southern border.

And in Iraq, the sectarian strife is as divisive as ever, with Iran dominating politics in Baghdad and the Ayatollah’s Shiite militias stoking fear in the hearts of the country’s Sunni minority even as the fighters function as the most effective force battling ISIS.

Through it all, Riyadh and Tehran haven’t yet squared off directly. That is, where Saudi Arabia has troops and planes Iran fights by proxy and where Iran has ground troops, the Saudis are fighting through their own proxies.

Saudi Arabia’s move to execute prominent Shiite cleric Nimr al-Nimr has the potential to change all of that.

The Sheikh was a leading voice among Saudi Arabia’s dissident Shiite minority and his death sparked outrage and street protests across the Shiite community. Riyadh cut diplomatic ties with Tehran after the Saudi embassy was torched in Iran and the Sunni monarchies quickly followed suit.

Meanwhile, Pentagon chief Ash Carter just can't seem to understand why the Sunni powers aren't more helpful in fighting ISIS. “It’s strange that a Sunni extremist group running rampant in Iraq and Syria should attract as little Sunni Arab counterweight as it has so far,” Carter told Bloomberg TV on Friday.

No, Mr. Carter, it is not "strange", nor is it a coincidence.

There is no "Sunni Arab counterweight" because Saudi Arabia promotes a similar brand of ultra puritanical Islam as that espoused by ISIS. Once again, if the US wants help in defeating Islamic State, Ash Carter may want to look to the nations that actually have a vested interest in bringing about the group's demise, namely Iran and Russia.

Prime Minister David Cameron acknowledged that Europe was experiencing "very great" pressure from migration and said the UK was "happy to do more" to strengthen external EU border controls, even though it is not part of the Schengen border-free zone which covers most of the continent.

Mr Valls said that European societies could be "totally destabilised" unless the EU imposes tighter controls at external borders. The French PM told the BBC: "It's Europe that could die, not the Schengen area. If Europe can't protect its own borders, it's the very idea of Europe that could be thrown into doubt. It could disappear, of course - the European project, not Europe itself, not our values, but the concept we have of Europe, that the founding fathers had of Europe. Yes, that is in very grave danger. That's why you need border guards, border controls on the external borders of the European Union."

He left little doubt that he believes German chancellor Angela Merkel's announcement last year that her country would welcome thousands of refugees had encouraged more people to come to Europe. "We need to help Germany," said the French PM. "But the main message we must send now with the greatest of firmness is to say that we will not take in all the refugees in Europe."

Daniel Yergin, founder of IHS Cambridge Energy Research Associates, said it is impossible for OPEC to knock out the US shale industry through a war of attrition even if it wants to, and even if large numbers of frackers fall by the wayside over coming months. Mr Yergin said groups with deep pockets such as Blackstone and Carlyle will take over the infrastructure when the distressed assets are cheap enough, and bide their time until the oil cycle turns.

“The management may change and the companies may change but the resources will still be there,” he told the Daily Telegraph. The great unknown is how quickly the industry can revive once the global glut starts to clear - perhaps in the second half of the year - but it will clearly be much faster than for the conventional oil.

“It takes $10 billion and five to ten years to launch a deep-water project.

"It takes $10 million and just 20 days to drill for shale,” he said, speaking at the World Economic Forum in Davos.

Harvard professor Ken Rogoff said China is the last big domino to fall as the global "debt supercycle" unwinds. This is likely to expose the sheer scale of malinvestment that has built up during the country's $26 trillion credit bubble.

Professor Rogoff said the official 1.5 percent rate of non-performing loans held by banks is fictitious. "People believe that as much as they believe the GDP data," he told the World Economic Forum in Davos. The real figure is between 6 percent and 8 percent. He warned that unexpected problems can come "jumping out of the woodwork" once a debt denouement unfolds in earnest.

Banks are disguising the damage by rolling over bad loans and pretending all is well, with the collusion of regulators, but this draws out the agony and ultimately furs up the financial arteries.

The ECB's president sought to play down the violent market squall of recent weeks, insisting that Europe's economic recovery is well on track and may even accelerate as the refugee crisis leads to a surge of fiscal spending. Signs that the ECB is preparing a fresh blast of stimulus have halted the increasingly ominous slide in global equities, but there are fears that the bounce of the last two days may soon fade.

Axel Weber, the former Bundesbank chief and now head of UBS, said the balance of advantage had already turned negative. "There is a very clear limit to what the ECB can achieve. The problem is that monetary policy has largely run its course," he said in Davos. "The side effects of the medicine are getting stronger and stronger: the curative effects are getting weaker and weaker," he said, adding that the current turmoil in the markets is the first taste of the hangover, evidence of the price we may have to pay.

“Today, there is approximately 50 billion kroner in circulation and [central bank] Norges Bank can only account for 40 percent of its use. That means that 60 percent of money usage is outside of any control. We believe that is due to under-the-table money and laundering,” bank executive Trond Bentestuen told VG.

“There are so many dangers and disadvantages associated with cash, we have concluded that it should be phased out,” he added. Bentestuen said that only around six percent of the Norwegian population uses cash daily, with the numbers higher amongst the elderly.

It is often thought that by choosing how we cook our spuds and greens, we either make a healthy or an unhealthy meal. Over the years, research has led us to believe that frying vegetables is a big no-no, and masks the antioxidant properties with a thick layer of fat. However, the results of a series of experiments have turned official advice on its head.

Research has found that potatoes and other vegetables kept more of their health-boosting compounds when fried in olive oil than when boiled in water. The study has proved that vegetables fried in extra virgin olive oil increased their anti-oxidant capacity and chemicals which prevent long-term diseases such as cancer, diabetes and loss of eyesight.

As five states saw snowfall of three feet (91cm) or more, the hazards of shovelling snow were brought home by at least six deaths. A further 12 people have died in other snow-related incidents since Friday. The storm, dubbed Snowmageddon and Snowzilla on social media, is weakening and heading for the Atlantic Ocean.

It has affected some 85 million people, cutting power to 200,000 people. The heaviest fall was recorded in Glengary, West Virginia, which had 42ins (107 cm). In Washington DC, the metro is set to remain closed and air travel in the region faces further disruption. Some 7,000 flights were cancelled this weekend and disruption is to continue into the working week, with at least 615 cancelled for Monday.

Sweden’s imposition of border checks on the Oresund bridge with Denmark, and the Danish government’s decision to do the same on its border with Germany, shows that the obstacles to a common response to the refugee crisis do not arise in central and eastern Europe alone. Nevertheless, it is the particular diagnosis of the problem in countries such as Hungary, Poland and Slovakia that distances them from their western partners.

Only Germany has the strength, strategic interest and sense of historical responsibility to prevent west and east from drifting apart. France is wrapped up in its unilaterally declared “war” on Islamist terror while the UK is wrestling with the question of Brexit — whether to leave the EU.

The political pressures on Ms Merkel from the refugee crisis will not abate: five of Germany’s 16 states will hold elections this year, and a federal election is due in 2017. The burden of responsibility on her and Germany’s political classes is heavy indeed.