Chris Atkins’ highly entertaining documentary about the soldier turned million-selling singer-songwriter effectively marks the apotheosis of James Blunt’s superb comeback – his rearguard action, in fact, against all the tabloid journalists, trolls and panel-show comics who were using him as a punchline, nettled at his overwhelming success and poshness.

Using skills honed at boarding school, and the possibilities of social media, Blunt neutralised the bullies by laughing at himself first, while also (with a dash of ruthless cunning) picking on civilians, quote-tweeting some member of the general public making a nasty remark and adding a very good gag notionally at his own expense but also embarrassing his tormentor. His Twitter game turned it around – though his sales never appear to have been really affected by the mockery. And throughout this fly-on-the-wall account of Blunt’s international tour, much delayed by Covid, the star retains a very droll and unashamedly well-bred irony, wit and down-to-earth attitude.

Blunt emerges from this film as a kind of pop Hugh Grant with a dash of Michael McIntyre – another supremely talented and successful individual who has had to endure envious scorn. And Blunt really does have an amazing personal story to tell: a serving British army officer who in 1999 was in danger of his life during the Kosovo war, and who then cheerfully pivoted to pop. There is a hilarious interview with his colossally megaposh parents and his dad dotingly remarks: “He enunciates well enough for the lyrics to be audible.”

Of course, those disposed to dislike Blunt will not be mollified by any of this, nor by the fan-worship of Ed Sheeran (interviewed here) who as a young boy was radicalised by seeing Blunt support Elton John at a stadium gig in Ipswich. It’s hard not to feel good for Blunt’s happy ending, but crowning him our newest national treasure might undo all his good social media PR work.

• James Blunt: One Brit Wonder screens on 6 December for one night only in UK and Irish cinemas.