There’s a painful, pentup anger and hurt at the heart of this documentary portrait of David Millar, the Scottish road-race cyclist and former Tour de France champ who was banned for doping in 2004 and, then became known as an anti-doping campaigner. It follows Millar as he prepares to take one last crack at the Tour de France, this time as a “clean” rider, thus preparing us for a Hollywoodised story of redemption. But it ends in his dreams being brutally and anticlimactically crushed; his team-leader drops him because he is not performing well enough – an awful implied comment on his entire past record, and just the kind of career gravestone inscription he was hoping to avoid.

The film immerses us in the (to my amateur eye) rather joyless business of grinding up and down hills and boiling with sweary resentment at other cyclists. Millar is shown at one stage having to be pulled over by his team to get his gloves on and jacket zipped up properly, like a miserable kid. Then there are taciturn “interviews” with Millar, who is captured in melodramatic shadowy darkness, a bit like Marlon Brando in Apocalypse Now. He clearly hates talking about the drug shame of the past, perhaps partly because it feels as if he’s reopening the wound and partly because, in the immortal words of Ronald Reagan: “If you’re explaining, you’re losing.” Winners let their success speak for them. It reminded me of that other notorious cycling drug cheat Lance Armstrong and his tight-lipped resentfulness in Alex Gibney’s film The Armstrong Lie – though Millar was always a lot more honest.

Finally we see Millar dancing in a club, evidently happy to be released from the terrible burden of competitive cycling. That image looks as if it has been tacked on to create something approaching a happy-ish ending. The reality may be a bit more downbeat.