It’s the bro-five. That moment when two like minded members of a brotherhood come together, outstretched hands colliding in a clasp somewhere between a high-five and a handshake.
If Mohammed bin Salman, the crown prince of Saudi Arabia, had any nerves about how he would be received at the G20 summit – his first major trip since being implicated in the murder of a dissident journalist – then Vladimir Putin’s warm but calculating greeting would have put him at ease.
The opening session on Friday was freighted with symbolism and vivid reminders of the realpolitik at work in Argentina. For world leaders are assembling at a time of extraordinary geopolitical turbulence, setting up a string of contentious clashes.
A looming Brexit, the new round of hostility between Russia and Ukraine, global trade wars and the fall-out from the killing of Jamal Khashoggi have officials struggling behind the scenes to find a joint statement that would rescue the summit from failure.
So an awkward air hung over the traditional “family photo” of prime ministers, presidents and princes. MBS, as the crown prince is known, found himself on the periphery, visibly and diplomatically, with empty space to either side at stage left. Theresa May, Emmanuel Macron and Justin Trudeau placed themselves to the right, where they could be sure not to catch his eye.
Picture done, MBS exited quickly. He was alone again minutes later standing at his allotted seat in the conference hall. And alone he might have remained, were it not for Mr Putin who swept in with that beaming smile and bro-five to remind the world that a Saudi with massive reserves of oil and a need for military defence systems is never long in want of an ally.
For all the public posturing, the criticism of MBS, the lining up of governments alongside Ukraine after its gunboats were seized by Russia, the anger at Mr Trump for his unilateralist foreign policy, the merry-go-round still has to spin.
Mrs May will still meet the crown prince even if Number 10 is avoiding saying whether or not she will shake his hand. And Mr Trump may well talk to Mr Putin even if he issued a very public tweet cancelling a planned, formal meeting.
It is a two-track summit. One designed for public consumption back home and the other, more discreet, calculated to get business done.
The same old game of public perception and private diplomacy as world leaders dance around the issues and each other. Just perhaps more so as a new breed of populist leader ups the ante.
But in this age of social media and cameras in every pocket, it is not an easy line to draw. You can imagine the delight of the Saudi foreign office when it published a photograph of Mr Macron chatting happily with the crown prince on the sidelines.
And then there is Mr Putin. Already at odds with the West, condemned for the Salisbury poisoning and facing additional sanction for seizing Ukrainian naval vessels at the weekend, he can burnish his domestic credentials with another display of independence and an embrace of MBS.