In Brussels it was bashing Angela Merkel, in London he did the dirty on Theresa May, what now lies in store when Donald Trump meets Vladimir Putin in Helsinki?

This is the question that has diplomatic observers guessing and doubtless has caused sleepless nights for some within the Trump administration as Monday’s summit meeting looms.

By any standards this will be an intriguing encounter, one likely to be a contest of theatrical power projection.

Despite Russia’s semi-pariah status among some Americans and US allies, notably Britain, the Kremlin has long been trying to arrange a summit.

For his part Mr Trump has been equally determined it will take place, despite serious reservations on behalf of his advisers and the long political shadow of alleged Russian interference over his 2016 presidential campaign.

Many US officials fear Trump will be out of his depth and prone to being played by a wily and astute Russian president.

Speaking to The New Yorker magazine this week, one former State Department official who spent decades preparing meetings between US and Russian leaders, summed up the view of many in Washington.

“I’m afraid our guy here is like an amateur boxer going up against Muhammad Ali,” the former aide warned.

While it’s one thing to lambast ‘allies,’ it’s quite another trying to throw your weigh around with a leader like Vladimir Putin certain US officials contend.

Some detractors suggest the very fact the summit is even happening is already a big geopolitical win for Mr Putin.

Since the breakup of the Soviet Union, some Russians have felt a palpable uncertainty about the country’s status as a global power.

Mr Putin’s support at home in part hinges on his ability to project power abroad, and Mr Trump’s desire to have the summit proves the US is no longer able dismiss Moscow.

According to Andrey Kortunov, Director General of the Russian International Affairs Council (RIAC), a foreign policy think-tank close to the Foreign Ministry, Mr Putin has “already got his victory.”

“It allows him to make his point that Russia is not isolated, that Russia is a great power, and to some extent can even claim an equal status with the United States, at least in the security field,” insists Mr Kortunov.

But while power projection and diplomatic choreography is one thing, the actual nuts and bolts of what the two presidents will address are something else.

There is certainly no shortage of contentious issues between the two countries and their leaders, but many observers remain puzzled as to why the meeting itself is taking place at this precise moment in time.

This uncertainty is compounded by the fact that Mr Trump has referred to the summit as “a loose meeting,” and there appears to be no substantive agreed advance agenda in place, another factor making some US officials vey apprehensive.

For what will almost certainly be one of the most crucial sessions of Mr Trump’s presidency there appears on the face of it to have been almost no preparation and a very short lead in time. Senior US officials say this is unprecedented in meetings between the president and his Russian counterpart.

According to journalist Susan B. Glasser who writes a ‘Life in Trump’s Washington’ column for The New Yorker, “one preparatory trip, no formal agenda, and no ‘deliverables’ is not normal for a summit between the heads of the world’s two biggest nuclear-armed nations.”

The fact that the single preparatory trip to Moscow was undertaken by Mr Trump’s hawkish national-security adviser, John Bolton, has only further added to speculation of what lies in store in Helsinki on Monday, and what deliverables if any, might be achieved.

Seen from Mr Putin’s perspective, on his wish list of those deliverables will be three things. The first will be seeking agreement with the Americans to stop pressing Russia over its intervention in Ukraine. Mr Putin might also like Mr Trump to make a renewed statement that Moscow had no part in interfering in the 2016 US presidential campaign. And then of course he would also like to see some relief from sanctions imposed on Russia.

For Mr Trump getting Moscow’s support in keeping the squeeze on North Korea, fighting international terrorism and securing some degree of adherence by Russia on international arms agreements would be on his wish list. Above all though getting Mr Putin’s help in dampening down the situation in Syria and allowing some space for opposition forces to remain intact will be of prime importance.

All this though as already said remains speculation, and given Mr Trump’s incendiary actions of late anything might go. If no grand bargain is on offer Mr Putin at the very least will get to look statesmanlike next to an unpredictable world leader.

As one US ambassador was quoted this week as saying about the Helsinki meeting following the debacle at the Nato summit in Brussels; “Everybody’s crossing their fingers and holding their breath.”