To all intents and purposes, Saudi Arabia and Israel are de facto allies in the struggle against Iran's rising influence in the region. It's a developing but highly sensitive relationship, but every so often there is a hint of what may be going on beneath the surface.
Last week Israel's Chief of Staff, General Gadi Eisenkot, said in an interview with UK-based Saudi newspaper Elaph, that Israel was ready to exchange intelligence with the Saudis in order to confront Iran.
"There are shared interests and as far as the Iranian axis is concerned we are in full accord with the Saudis," he said.
A few days later, speaking after a conference in Paris, a former Saudi justice minister, Dr Muhammad bin Abdul Karim Issa - a close associate of the Saudi Crown Prince Mohammed bin Salman - told the Israeli newspaper Maariv that "no act of violence or terror that tries to justify itself by invoking the religion of Islam is justified anywhere, including in Israel".
This was rare public criticism from inside the Arab world of attacks against Israelis.
And just the other day a former senior Israeli military figure speaking in London told of two recent meetings with senior Saudi princes, both of whom said to him words to the effect that, "you are not our enemy any more".
Such signals are not sent by accident. They are carefully co-ordinated and intended to warn Iran of the developing relationship as well as to prepare Saudi society given the likelihood that such ties may become ever more apparent.
The Israelis - given the nature of their political culture - tend to speak rather more openly about the relationship than do the Saudis. We know little about its practical realities or its strategic content. But it is real and it is developing.
Threat from Iran
This is at one level "a coalition of circumstance". The destruction of Saddam Hussein's regime in Iraq in 2003 by a US-led coalition removed a Sunni Arab strategic counterweight to Shia Iran.
The resulting Shia-dominated political leadership in the new Iraq has close ties to Tehran. It is no accident that Iraqi Shia militias have been active in the fighting in Syria supporting the government of Bashar al-Assad.
Iran's decision to back President Assad in the Syrian civil war, along with Russian air power and equipment, helped turn the tide in his favour. It opens up the possibility of an Iranian corridor stretching all the way from Tehran to the Mediterranean - something that many Sunnis see as a foreign, Persian intrusion into the heart of the Arab Middle East.
So the enmity between Iran and Saudi Arabia is both strategic and religious.
For the moment Iran and its allies and proxies, like the Shia militia group Hezbollah in Lebanon, appear to be winning. So a strengthening of the relationship between Israel and Saudi Arabia makes sense to both countries.
Both insist that Iran should never be allowed to become a nuclear weapons state. Both are uneasy about aspects of the international agreement limiting Iran's nuclear activities. And both see an increasingly well-trained and well-equipped Hezbollah in Lebanon as a force for instability in the region.
But there is something more going on here as well. It is not just the problem of a rising Iran. Other crucial factors need to be considered too, notably the impact of the new Trump administration in the United States and the broader trajectory of the Middle East in the wake of the Arab Spring and the horrific war in Syria.
At first sight neither Saudi Arabia nor Israel should have any complaints about the new administration in Washington.
Mr Trump in visits to both countries seems to have embraced their strategic outlook and he too is deeply sceptical about the nuclear agreement with Iran.
He is lavishing Washington's allies in the Gulf with new arms sales of ever more sophisticated weaponry.
But empathy is one thing, practical strategy quite another. However welcome many of the president's words may be in Israel and Saudi Arabia, both governments know that US policy seems adrift in the region.
The US and its allies have been out-gunned and out-played in Syria by Russia and Iran.
For all the talk the US has not yet put forward a credible and coherent policy for containing Iranian influence.
No wonder the Saudi Crown Prince has decided that his country must be more active in its own interests. There is a sense in which both Israel and Saudi Arabia are adjusting to a waning of US influence in the region and the return of old actors like Russia.
And there is something more fundamental too. Prince Mohammed is embarking on a dual strategy of trying to confront Iranian influence while also re-shaping and modernising the kingdom.
The latter is in many ways a response to the upheavals of the Arab Spring and the threat of Islamist violence.
Prince Mohammed appears to have determined that the region must change if it is to have any future. And change begins at home. Reform may be as important as containing Iran.
A number of private discussions lead me to believe that this is something that Israel buys into too. They recognise that Prince Mohammed's activism comes with many risks.
But they have watched with horror from the sidelines of the war in Syria, not least at what some Israelis see as the "normalisation" of the use of chemical weapons; this prompting a very limited response from the wider international community with Moscow actually lending its protection at the UN Security Council to its Syrian ally.
Israelis see Syria as "a laboratory" of what could be the region's future. Hence their willingness to stress the positives in what Prince Mohammed is trying to do.
How far might this Israeli-Saudi dynamic go? Well that depends upon a lot of factors. Will Crown Prince Mohammed's bold attempt to change Saudi Arabia's course succeed? Might he over-reach in terms of Saudi Arabia's effort to exert regional influence?
Fundamentally, if the Saudi-Israel relationship is to emerge blinking into the sunlight, there needs to be progress on the Palestinian front. The Saudis have long said this must come before they will openly recognise Israel.
Without the renewal of a meaningful peace process that actually promises Palestinian statehood the Saudi-Israel "alliance" must remain in the shadows.