Donald Trump arrives in London next week for a two-day Nato summit which will see him greeted on Tuesday evening by doctors, nurses and other NHS workers leading a protest of tens of thousands outside Buckingham Palace.

The protesters – aiming to highlight potential risks to the NHS in a future US-UK trade deal – will march from Trafalgar Square up the Mall, and gather at Canada Gate when Trump and other Nato leaders meet the Queen at a 6pm drinks reception.

It will mark the formal beginning of a short summit that has been in the diary for 18 months, but has ended up occurring at the closing stages of an election campaign, prompting jitters in No 10 – and making for Labour’s best hope of a comeback.

Boris Johnson pleaded with Trump not to wade into British politics in an interview on LBC: “It’s best when you have close friends and allies like the US and the UK … for neither side to be involved in each other’s election campaigns.”

Labour is preparing for something different, mindful of the fact Trump can rarely be relied upon to exercise discretion. The last time the US president was in the UK in June, he said that “everything is on the table” – including the NHS – in trade talks.

It is not yet clear if Corbyn himself will address the London demonstration, which will begin at around 4pm in Trafalgar Square. Confirmed speakers for the event include veteran activist Tariq Ali, musician Brian Eno, and Kate Hudson, the head of CND, although the Trump baby blimp is not expected to make a reappearance.

The Labour leader is expected to give a foreign policy speech on Sunday, aimed squarely at Trump, and has accused Johnson of putting the NHS “on the table” in “secret talks for a deal with Donald Trump after Brexit”.

On Friday, Johnson responded, insisting that the NHS is “not for sale or up for negotiation” in any future trade talks.

Trump is arriving late on Monday night, leaving the president free time on Tuesday before the Palace reception for bilateral meetings but also media interviews, possibly with Piers Morgan on ITV or Nigel Farage on LBC.

The leaders – including, presumably Trump – will then go from Buckingham Palace to Downing Street for a second reception on Tuesday evening, this time hosted by Johnson. Downing Street has yet to release details, but other European leaders said they expected to be present.

On Wednesday the leaders will head to the luxury Grove hotel on the outskirts of Watford, a past base for England football teams ahead of World Cups, where Trump is scheduled to give a press conference on Wednesday afternoon, almost immediately after a separate press conference from Johnson.

The summit has already been deliberately stripped down so that its main purpose is ceremonial, focusing on the 70th anniversary of an alliance whose first headquarters was in the UK, to reduce the potential for diplomatic rows.

Receptions and press events aside, its only substantive business is a three-hour session at the Grove hotel on Wednesday morning where each leader is due to speak for four minutes, a cumbersome format that Nato says acts as a useful opportunity to raise key points.

Nor is Trump the only complication. Turkey’s president Recep Tayyip Erdoğan is due to attend, a month after his country’s invasion of the Kurdish region of Syria, and has already been sparring with France’s Emmanuel Macron.

Erdoğan asked Macron to “check whether you are brain dead” after the French leader had argued that Nato was failing to provide strategic coordination between the US, Europe and Turkey.

Nonetheless, Nato officials were already expecting Trump to dominate proceedings. “What can we do? It’s a leaders summit after all,” one said ahead of the meeting, although the question may be what topic will the unpredictable president chose to pick up.

At the last leaders’ summit, in Brussels in July 2018, the US president ripped up the schedule, and demanded that Europeans spend more on defence – or the US would walk out of the 70-year military alliance and “go it alone”.

This time Nato, eager to demonstrate concrete progress, released spending figures showing that allies increased defence spending by 4.6% in real terms, and that a growing minority of its 29 members were meeting long-term spending promises.

“More allies are meeting the guideline of spending 2% of GDP on defence,” Jens Stoltenberg, Nato’s secretary general, told a press conference. “This year, nine allies will meet the guideline. Up from just three allies a few years ago.”

The UK, at 2.1%, already meets the target, although the US spends 3.4%. But such efforts are unlikely to be enough to ensure a harmonious summit eight days before Britain goes to the polls.