Motor racing can, it seems, generate endless stories to interest even those who come out in hives at the sight of a chequered flag. Following in the wake of Senna, Rush and Road, we now get a fascinating documentary on (for once the tagline deserves repetition) the greatest racing driver you've never heard of.

Now 58, Tommy Byrne, a Drogheda man, excelled in Formula Ford and Formula Three during the early 1980s. Eddie Jordan, interviewed here, confirms that few drivers had an ounce of Byrne’s talent. But he never quite made it in the big time.

A rough period in Formula One with a minor team was followed by a return to the minors and, eventually, an opportunity to test for McLaren. That elite team, wary of such a volatile personality, turned him down. An indifferent career followed in Mexico and the US. Byrne now lives in Florida and works as a racing-driver coach in the midwest.

Aggressive, articulate, not without charm, Byrne is an ideal subject for a documentary. He is a sinner who was greatly sinned against. Seán Ó Cualáin, the director of Men at Lunch, lucidly walks us through the snobbery and love of money that characterises motor racing.

No other sport demands such indecent sums from young competitors. The penniless Byrne was so talented that he managed to get drives “for free”, but he couldn’t muster the submission to authority needed for further advance (did we mention he was from Louth?).

Then there was his taste for sex, drugs and booze. Jordan suggests that, had he played the game, Byrne may well have risen to the very top, despite McLaren’s snittiness. Happily, Byrne appears to have found peace now.

Ó Cualáin tells his story with great economy. The interviewees are frank and lucid. The archive footage is copious. It is hardly worth mentioning that, as is the case with too many contemporary documentaries, empty spaces are filled with adequate, if undistinguished, animated sequences.

A great yarn. A great education.