As he boarded the night train to Ukraine, Boris Johnson had the usual entourage of aides and bodyguards – plus the man who had given him £1m.

Less than a year had passed since Johnson accepted what is thought to be the largest donation ever to an individual MP. It was from Christopher Harborne, one of the UK’s biggest and most private political donors.

Harborne, whose millions helped bankroll Brexit, made the payment to a private company Johnson set up after resigning as prime minister. Now leaked files show that Johnson, a champion of Ukraine in office and since, was accompanied in September 2023 by his benefactor on a two-day visit that included meetings with top officials.

What the files do not explain is why. And neither the former prime minister nor his backer will say.

The organisers of the high-level gathering they attended in Kyiv say Harborne was registered as “adviser, Office of Boris Johnson”.

Harborne has wide expertise: a self-described “digital nomad”, his holdings range from cryptocurrency and a wellness centre to jet fuel and stakes in at least three military contractors. His only apparent connection to Ukraine is as the biggest shareholder in a British weapons manufacturer whose robots and drones are reportedly supplied to its armed forces.

The Boris Files, leaked documents from Johnson’s private office, have exposed how he has sought to enrich himself since leaving office by sitting down with a Venezuelan despot and courting Mohammed bin Salman, the Saudi crown prince accused of ordering the murder of a journalist.

The Ukrainian cause, by contrast, is “sacred” to Johnson, one political consultant says, an enduring source of moral authority for a politician who was forced out of Downing Street amid scandal.

The leaked files raise questions about whether, even here, he has blurred the lines between public service and money-making.

Boris Johnson (front left) and Volodymyr Zelenskyy (centre) during Johnson and Harborne’s trip in September 2023. Photograph: Sergey Illin/Victor Pinchuk Foundation©2023

In an extraordinary statement to the Guardian when asked about his relationship with Harborne, Johnson said: “Your pathetic non-stories … seem mostly to be derived from some illegal Russian hack job. You should be ashamed of yourselves.” Distributed Denial of Secrets (DDoS), the US-based transparency group that obtained the leaked files, said it did not know their provenance.

Johnson added: “Why don’t you just change your name to Pravda? Your stories are rubbish and you are doing Putin’s work.”

‘Boris and Chris only’

In Downing Street, Johnson rallied western powers as Vladimir Putin’s armies poured into Ukraine in February 2022. Since resigning, he has continued to travel there, pledging to maintain allies’ commitment, and remains so popular that he is cheered in the streets.

When he disembarked from the night train in Kyiv on 8 September 2023, Johnson had time for a quick shower at his hotel before heading for the Yalta European Strategy (YES) forum, an itinerary in the leaked files indicates. According to a published list of participants, Ukrainian ministers, spymasters and military chiefs mingled with foreign diplomats, politicians, industrialists and executives.

The itinerary has “Boris and Chris [Harborne] only” down to attend the opening session of the high-level gathering. Images show Volodymyr Zelenskyy and Johnson addressed the gathered luminaries and the itinerary suggests they then retired for a private meeting. Zelenskyy’s office did not respond when asked if Johnson’s benefactor joined them.

Afterwards, Zelenskyy posted a picture of himself with Johnson. “From the first hours of the full-scale war, Boris Johnson sincerely supports Ukraine and helps defend against Russian aggression,” Zelenskyy wrote. “And now continues to add international support to Ukraine. Thank you for your energy, friend!”

Johnson’s itinerary says he had further meetings scheduled that day with Zelenskyy’s foreign minister, who said he could not recall whether Harborne attended, and the oligarch who runs the forum.

The next day Johnson headed west to Lviv to lay flowers at war graves, visit the wounded and receive an honorary degree. Footage shows Harborne standing nearby as Johnson greets troops. A photograph shows a meeting with another senior Ukrainian official, Lviv’s mayor, Andriy Sadovyy. Harborne looks on while Johnson holds court.

Boris Johnson (centre) meeting Lviv’s mayor (1st to his left) in September 2023 with Christopher Harborne (2nd to his right). Photograph: City of LvivThe £1m donation

In a recent court filing against the Wall Street Journal, Harborne calls himself an “intensely private person”. Although he has lived in Thailand for more than 20 years, holds a Thai passport and sometimes goes by a Thai name, Harborne has put considerable money into British politics.

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He has given £10m to Nigel Farage’s Brexit party – now Reform UK – and £1m to the Conservatives while Johnson was completing the UK’s departure from the EU. And Johnson seems to have nurtured the beneficial relationship while he was in No 10.

Harborne visited Chequers at least twice during Johnon’s premiership. Once, he arrived at the prime ministerial retreat by helicopter. The second time was for a Tory megadonor barbecue in August 2022.

Within days, Johnson’s tenure was over, but his relationship with Harborne endured, and the £1m gift followed. A copy of the financial advice Johnson received soon after leaving Downing Street raises questions about it.

Volodymyr Zelenskyy: “Thank you for your energy, friend!” Photograph: Volodymyr Zelenskyy/Telegram

While Johnson was still an MP he set up a private company, The Office of Boris Johnson Ltd. The financial advice reveals that he was expecting a “payment to fund the company’s first few years”. He was advised to consider whether this would represent a political donation or if it “might be simpler for the company to invoice the donor’s company for services”.

The following month, in November 2022, Johnson’s entry in the register of MPs’ interests records a £1m donation to his company from Harborne. The payment does not appear on the Electoral Commission’s donation database of money “given towards the recipient’s political activities” as an MP. This appears to suggest it may have been a contribution towards Johnson’s money-making activities.

The month of the £1m payment, Johnson and Harborne dined together twice in Singapore. A January 2023 entry in Johnson’s schedule set aside half an hour for a call with his backer. It was labelled “Ukraine readout”. That September, by which time Johnson had quit parliament, he and Harborne stepped aboard a Dassault Falcon at Stansted airport, the leaked files indicate. The private jet, apparently operated by Harborne, carried them to eastern Poland to catch the sleeper to Kyiv.

Harborne’s lawyers said: “Mr Harborne’s donation was given to enable Mr Johnson to stay actively engaged in mainstream UK politics. It is and was a donation, and its reporting as such is appropriate.”

They added: “Mr Harborne had and has no expectation of personal gain whatsoever. Any suggestion otherwise is completely without evidence and materially and knowingly false.”

The letter

Harborne’s lawyers did not give substantive answers to questions about why he went on the trip to Ukraine, beyond saying they “appear to have little to no basis in reality”. But there are possible clues in the leaked files.

The itinerary features a “closed meeting at the military-tech R&D centre”. It does not say whether Harborne attended, but this is an area he knows well. While his position as the largest shareholder in QinetiQ, with 13%, does not give him a role in the day-to-day running of the privatised research unit of the UK armed forces, his financial stake in its operations is significant.

QinetiQ has interests in Ukraine, albeit not its biggest. Ukraine’s forces reportedly use the company’s Banshee drones and bomb-disposal robots. In April 2025, the UK Ministry of Defence announced QinetiQ would help Ukraine’s military make kit with 3D printers.

Johnson refers to the trip in one of the Boris Files’ more mysterious documents. Dated 23 October 2023, the month after the visit, it is a letter carrying his signature. “I write in support of Christopher Harborne,” Johnson writes. “He is both a friend and a supporter of my office … He came with me on a recent trip to Ukraine and I know him to be a passionate opponent of the Putin regime.”

Johnson states in the letter that he is “aware of no suggestion or evidence whatsoever that Christopher is in any way supportive of the Russian government, or has links to Russia commercial or otherwise”. There is nothing to indicate why anyone might think otherwise. No such connections have emerged and Harborne’s lawyers say none exist.

The lawyers would not say who the letter, addressed only to “Dear Sirs”, was written for. “Mr Johnson provided a character reference for Mr Harborne in response to attacks on Mr Harborne’s character,” they said. “Mr Harborne is grateful to Mr Johnson.”