There’s a revealing moment in the 2015 BBC documentary Bad Reputation, included here, in which Phil Lynott talks about his attitude to fame. “I was tired of hearing stars feeling sorry for themselves and saying they disliked being famous,” he drawls in his twinkling Dublin brogue. “I jumped at it. The women are after me, people want to buy me free drinks, to treat me, take me here and there. Great! I went for it hook, line and sinker.”

It seems to encapsulate what made Thin Lizzy, and what destroyed them. The enjoyment, energy and passion with which Lynott and his compadres embraced the rock’n’roll life oozes from every track on this 6CD+DVD set, released to mark the 50th anniversary of the band’s first recording contract.

Later in the same film Bob Geldof remarks that he has never met anyone who “enjoyed being a rock star so much” as Lynott did, while Scott Gorham, one half of the band’s famous twin guitar attack, notes with a mix of admiration and horror that Lynott “could take more drugs, screw more chicks, stay up more days in a row than anyone else”. Yet if Lynott took his partying seriously, he applied an even greater dedication to his music. Every one of the musicians who passed through Thin Lizzy’s ranks between 1970 and 1983 attests to Lynott’s work ethic. The determination to put out his best on every occasion even led to a flawless soundcheck performance ending up on 1978’s Live And Dangerous. There was never any going through the motions; it was always “hook, line and sinker” – and there’s ample evidence of it here, spread across 99 tracks, an impressive 74 of which are previously unreleased.

Disc One starts in familiar territory and acts as an essential Lizzy primer with crisp, three-minute radio edits of 22 hits from “Whiskey In The Jar” and “The Rocker” to “The Boys Are Back In Town” and “Dancing In The Moonlight”. Such tracks are the sine qua non of any collection, but it’s on Disc Two that things start getting interesting with 17 deep and mostly unreleased tracks from the band’s Decca years between 1971 and ’74. Highlights include a never-heard-before six-minute extended “Whiskey In The Jar” with some lovely harmonic guitar soloing from Eric Bell and extemporised vocals from Lynott on the fade-out, and a rough and ready acetate of a raucous 12-bar blues with screeching slide guitar titled “Baby’s Been Messin’”: it later emerged in different form as “Suicide” on 1975’s Fighting.

Elsewhere a brace of Radio Eireann sessions recorded a year apart illustrate the speed of the band’s progression. The first from January 1973 finds Lizzy as standard period blues-rockers, sounding like a Rory Gallagher tribute act on non-album tracks such as “1969 Rock” and a jam with Real McCoy guitarist Eddie Campbell titled “Eddie’s Blues/Blue Shadows”. Yet by the time of the second session exactly 12 months later, the confidence and swagger have undergone a quantum leap and they sound like a different band on the jazzy “Ghetto Woman” and a storming cover of Freddie King’s “Going Down”.

We then get three discs containing demos for 49 songs recorded while they made nine classic albums, from 1974’s Nightlife to 1983 swansong Thunder And Lightning. It might have been fascinating to hear solo demos of the songs by Lynott, but what we get are essentially fully worked-out band versions with the twin harmony guitars in full flow; they hardly sound like demos at all and more or less match the familiar album cuts. Put it down as another indication of how professional rigour marched hand-in-hand with freewheeling hedonism.

Among the well-known, however, are a number of unreleased songs. “Blackmail”, originally slated for Black Rose, is a classic hard rocker, while the slyly syncopated “It’s Going Wrong” has a terrific lyric and vocal which finds Lynott at his most playful. “Kill”, co-written with Rick Parfitt, sounds more like Status Quo than Lizzy, but “In The Delta”, a swamp-rock jam with Huey Lewis on harmonica, and the synth-laden melodrama of “Don’t Let Him Slip Away”, cut during the Thunder And Lightning sessions, are lost gems.

The final disc was recorded live over two high-octane nights at the Hammersmith Odeon in May 1980, capturing Lizzy halfway between 1978’s Live And Dangerous and Life, recorded on their 1983 farewell tour. By the time the opener “Are You Ready” has finished, you can already sense the sweat rolling down Lynott’s face.

A good boxset doesn’t have to be rammed with startling new revelations and, in truth, there are only a handful here; but if the purpose is to make you fall in love with a long-cherished band all over again, consider it mission accomplished.

Extras: 8/10. DVD featuring the Bad Reputation doc and the band’s performance on Rod Stewart’s 1976 A Night On The Town TV Special; replicas of tour programmes; booklet with recollections by members plus quotes from famous fans from Slash and Bobby Gillespie to John McEnroe.