Former Prime Minister David Cameron has disclosed that he offered Boris Johnson a senior cabinet role in an effort to secure his support for the UK remaining in the European Union during the 2016 referendum. The revelation comes as part of a BBC documentary marking the 10th anniversary of the Brexit vote.

Cameron said he proposed Johnson a “top five” government position, such as defence secretary, on the condition that he would not endorse the Leave campaign. Johnson’s public decision to back Brexit in early 2016 significantly shifted the dynamics of the referendum debate, occurring just four months prior to the vote.

Recounting the conversation, Johnson said that Cameron invited him for a tennis match at the US ambassador’s court near Regent’s Park in central London, where the prime minister raised the prospect of Johnson joining the Remain campaign and taking a senior cabinet role. Johnson described his curiosity about the offer, wondering what the elusive “top five” job entailed, referencing the known senior posts of prime minister, chancellor, home secretary, and foreign secretary.

Cameron later clarified that he did not specify the exact position but cited defence secretary as an example of a top-tier role to emphasize his desire to keep Johnson instrumental within government. Cameron indicated that the offer was meant to signal how much he valued Johnson’s political influence and wished to keep him engaged within the administration.

Craig Oliver, who was Cameron’s director of communications at the time, recounted that the prime minister left the meeting feeling optimistic for two reasons: his victory on the tennis court and the prospect that Johnson might join the government’s pro-Remain efforts.

Despite the offer, Johnson ultimately broke ranks and publicly supported the Leave campaign, a decision that proved a major setback for Cameron. On the day Johnson’s stance was made public, Cameron reportedly urged him not to align with Leave campaigners Nigel Farage and George Galloway. Around the same time, Michael Gove, then justice secretary and a close ally of Johnson, had already announced his support for Brexit.

The BBC is airing the first episode of a two-part documentary titled Brexit: A Very British Civil War on Monday, which explores these critical moments in the lead-up to the referendum.