On January 23, 1975 Mick Jagger stood in the arrivals hall at Rotterdam airport on the look-out for a long-haired Irishman in a checked shirt.

Eventually he spotted Rory Gallagher, the 26-year-old guitar wizard from Cork, fresh off a flight from Heathrow. Gallagher walked slowly through arrivals, hefting a suitcase, his battered 1961 Fender Stratocaster and an amplifier. He and Jagger went outside to a taxi rank.

Jagger and a cabbie haggled over the price of the 15 minute drive back to De Doelen Concert Hall, close to Rotterdam Centraal train station. Bombed into oblivion during the war, the 2,200 capacity venue had been rebuilt in 1966. Now it was playing host to a different kind of conflict, as the Stones rehearsed for their upcoming tour.

This was to be their first since the surprise departure that December of guitarist Mick Taylor (who had in turn replaced founding member Brian Jones in 1969). Gallagher was in the Netherlands to audition for the berth vacated by Taylor. Later that evening he stepped onto the cavernous De Doelen stage, his footsteps echoing in the floorboards.

There to meet him were the rest of the Stones, with the exception of Keith Richards who was missing and presumed to be off his face somewhere. Stones manager Marshall Chess Jnr stood forward and proffered a hand.

"Hi Rory, welcome to the band," he said. "You're the guy for the job."

This was just one extraordinary chapter in the life of Gallagher, who passed away 25 years ago this month following complications from a liver transplant. During his life Gallagher was a cult figure among other guitarists, who were awestruck by the virtuosity and sheer ferocity of his playing.

The fan club included Eric Clapton and Ginger Baker, who took him on the road as support for Blind Faith's epic summer 1969 trek around America. Johnny Marr of the Smiths and Slash from Guns ' n' Roses were admirers too.

One apocryphal story has Jimi Hendrix being button-holed backstage at the Isle of Wight Festival and asked how it felt to be the world's greatest guitarist. "Go ask Rory Gallagher," he is reputed to have said without missing a beat.

But by the time of his passing Gallagher had fallen from fashion. He died, if not in obscurity, then very much on the slope downwards. "He definitely felt himself he had been forgotten a bit," says Daniel Gallagher, Rory's nephew, who was 13 when the guitarist succumbed to a post-operation infection. "He wasn't a self-publicist. He didn't understand idea that he had to sell himself or release singles."

Daniel recalls an interview Cameron Crowe, the Rolling Stone journalist turned film director, once gave about Gallagher. Rory was on a publicity jaunt across America and Crowe tagged along to write about it. "He hated doing PR. Every day he would go back to his hotel after a day of schmoozing and he would be exhausted. It drained him."

"In the Eighties and Nineties, he was almost airbrushed from the rock scene," continues Rory's brother Dónal. "In a way it skipped a generation. Young people now seem to enjoy the performances, his integrity.

"I always put it down to the fact that he didn't do singles - he didn't go down that route of miming on Top of the Pops. He would do his share of press. But whenever he was asked about himself he would refer to another, overlooked guitarist: Doc Watson or Django Reinhardt, perhaps."

Punk and its scorched earth repudiation of the music that came before didn't help, says Dónal. "It gals me. The Old Grey Whistle Test made three specials about Rory - the only artist they ever did that for. And yet they never show them. Johnny Rotten was a fan [Rotten, aka John Lydon, had family connections to Gallagher's native Cork].

"The Clash would always credit him. But he had been named the best guitarist in the world by Melody Maker and that made him a target for the NME. If you were a Melody Maker artist, the NME regarded you as old and boring."

Twenty-five years from his death, things have turned full circle. Gallagher has been discovered anew and taken his rightful place alongside rock gods such as Eric Clapton, Jimmy Page and Jeff Beck. He's starting to sell in respectable numbers, too. A recent live album, Check Shirt Wizard: Live In '77, made the UK top 40; a 2019 collection of Gallagher blues covers topped the Billboard blues chart in the USA. And footage of Gallagher's searing 1970 Isle of Wight performance with his band Taste has clocked up millions of views.

In the Isle of Wight clips, Gallagher is a force of nature. He doesn't seem to play guitar so much as wrestle it, as if trying to tame a wild beast. "With Rory it was always teetering on the brink...With Cream, for example, there was no danger. Everything Clapton played was perfect and you knew it was going to work," Gallagher's long-serving bassist Gerry McAvoy wrote in his autobiography, Riding Shotgun. "Clapton may have been a better technician but Rory was certainly more exciting. He would take chances that Eric just wouldn't take."

One milestone he never achieved, though, was joining the Stones. The mid-Seventies had been a testing period for the rock's original wild bunch. Richards was in the throes of cocaine addiction; Mick Taylor had sensationally walked out in the middle of the recording of their Black and Blue album. Taylor had felt his contribution, especially in the studio, had not been acknowledged. Increasingly dependent on heroin he worried, too, that the Stones lifestyle was leading him on a path to destruction. If he didn't leave he feared the worst. He wasn't built like Jagger and Richards. He broke the news to Jagger at a party on December 12 1974.

"To ask if I regret leaving the Rolling Stones is to ask the wrong question," Taylor would later state. "The hard one to answer is, do I regret joining them?" The timing was unfortunate. Sessions for Black and Blue were ongoing. And the Stones were booked for a lucrative North American tour starting in Baton Rouge on June 1 1975. So they needed a new guitarist and quickly. Rory Gallagher was the first name on their wish-list.

"Mick Jagger had always been very vocal about how he admired Rory's playing," says Dónal, who together with Daniel, his son, has worked tirelessly to keep Gallagher's legacy alive. "And when the Rolling Stones first formed their own record label, Keith Richards made it clear that the two people they wanted to sign were Rory Gallagher and Peter Tosh."

Gallagher was born in Donegal but grew up in Cork, Ireland's fiercely independent second city, with a music scene that has always existed apart from that of the rest of the country. Based in London for most of his career, he and Dónal happened to be home for Christmas and staying with their mother in Douglas, on Cork's southside, when the phone rang one night late in 1974.

"It was about one o'clock the morning," recalls Dónal. "Back then, if the call was overseas you had to go through the operator. She told my mother she was connecting. I took the call. I was a bit defensive because in those days there were a lot of kidnappings [by the Provisional IRA]. The guy says, 'my name is Ian Stewart...I'm looking for Rory Gallagher."

Stewart co-founded the Rolling Stones with Brian Jones in 1962. However, he had been notoriously shunted from the line-up by the Stones's early manager Andrew Loog Oldham, who felt he did not fit their bad boy image. He stayed on as road manager, keyboardist and general fixer. It was in that last capacity that he was placing a call to the southside of Cork city a few days before Christmas. "Rory had gone to bed on one of his rare early nights," recalls Dónal. "When I woke him he thought I was winding him up. But he agreed to go to Rotterdam to jam with them."

Sensing a once in a lifetime opportunity, Dónal was keen to accompany his brother to offer advice and emotional support. Gallagher, however, was reluctant to become too excited. "I said to Rory, "please let me go, this is serious". He said "no, it's only a jam session". To which I responded, "if they have a mobile unit and they're recording you...it's serious".

The problem was that Keith Richards was absent both in body and mind during Gallagher's audition. "He was going through a pretty bad time from what I understand," says Dónal. "The first night Rory was there he didn't come down at all." Richards was in his elegantly wasted prime, with the emphasis more on wasted than elegant. Playing Knebworth the following year, he was in such a state that his road crew cut the wires to the speaker system.

This caused a 90 minute delay, during which they tried to revive him. After the show he fell asleep snorting heroin at the wheel of his Bentley and crashed into the central reservation of the M1. When people wonder how Richards is still alive, this is the period they are talking about.

It was an indication of the Stones's dysfunction that, though Jagger seemed amenable to having Gallagher join, he didn't feel able to discuss it directly with Richards. Instead at the end of three days of rehearsals at De Doelen he drew Gallagher aside and advised he speak to Keith. The complicating factor for Gallagher was that he had booked a Japanese tour and needed to get back to Heathrow the following day if he was to make the dates. He was a huge star in Japan at the time and didn't believe in letting down his audience. The clock was ticking.

"Rory went up to Keith's suite. Keith was passed out," says Dónal Gallagher. "Rory stayed up all night and would go up every half hour to see if he'd woken up." With Richards out of it, the next morning Gallagher said his goodbyes, took his amp and guitar and left.

In March Ronnie Wood of The Faces flew out to meet Mick and Keith. On April 14 he was unveiled as Taylor's replacement (though he didn't become an "official" member until February 1976). After Gallagher, the band had also auditioned Peter Frampton, Wayne Perkins, Jeff Beck and Steve Marriott. But Rory was first on their list.

Would Gallagher have played well with the Glimmer Twins? Bill Wyman, the Stones's bassist at the time, wasn't so sure. "Rory stayed two or three days there and played some nice stuff," he said later.

"We had a good time with him but I think Mick and Keith felt that he wasn't the kind of character that would have fit. If he'd been in the Stones he wouldn't have been singing and that was one of his strong points. He would have just been playing solos.. and learning to be subservient to the two big egos. I don't think it would have worked."

"He could never have put up with the b______s of Mick and Keith," opined Bob Geldof, who knew both parties, in Ian Thuillier's 2010 documentary, Ghost Blues: The Story of Rory Gallagher. "Never in a thousand years. Up against Mick and Keith he would have shot himself. "

Larry Kirwan, of Celtic punk-band Black 47, had a different take when talking to Thuillier. "He could have single-handedly revived their creative spark," he said. "Imagine Keef trying to keep up with this bluesy dynamo. What a power duo they would have made... intertwining rhythm and lead lines. They were born for each other."

Gallagher himself came across as ambivalent about joining the Mick 'n Keef circus. He certainly did not feel he had squandered the opportunity of a lifetime. "If somebody needed a guitar player for a tour and I was free and it was the right situation, I'd do it and it would be good fun," he shrugged. "There would be much less pressure if I just had to stand there and play leads."