Once inside the bar, whose facilities included urinals that had been installed but never plumbed in, our party's arrival excited a lively response from the regulars, who engaged us in friendly conversation for a couple of hours. Then - influenced, perhaps, by the torrent of Victoria beer and mescal - the atmosphere took on a character of mounting hostility, which became unmistakable even to the more exhilarated foreign visitor when our one fluent Spanish speaker began to interpret phrases such as "knife fight".
At the height of our unease a guitar appeared in the way that they do - seemingly by magic - in Elvis Presley musicals. Croker picked it up and sang them Hank Williams's "Your Cheatin' Heart". It was a high-risk strategy, but within the first few bars of the song - which he followed with the Jim Reeves number "He'll Have to Go" - I could sense a second volte-face by our fellow-drinkers, this time from psychotic loathing to a kind of transfixed awe. We then left immediately, our would-be assassins' leader discreetly pressing an unsolicited packet of hashish into the singer's hand on the way out.
"I'm really glad we went in there," Croker told me, out in the street. "Mexico - what a fine country. What a busy people."
First impressions can be misleading, of course, but the incident illustrates a number of Brendan Croker's qualities, not least his convivial nature, his fondness for adventure, and the emotional power of a singing voice that has an affecting combination of roughness and sensitivity.
The term "maverick" might have been invented for Croker. Over the past 15 years, he has produced a number of breathtaking rhythm and blues and country-influenced recordings, and is admired by such figures as Eric Clapton, John Mayall, and his frequent collaborator Mark Knopfler.
"He is a world-class songwriter," says his long-term ally Andy Kershaw, "and a tremendous singer. I have always thought of him as a British Ry Cooder. He has one of those rare voices that sound almost black. If Brendan Croker had surfaced in Muscle Shoals, Alabama, in 1969, instead of Yorkshire in 1979, he'd have made a bigger impact than he has."
I met up with Croker again earlier this week in the bar area of a Pizza Express in central London. The arrival of the 45-year-old, with shaven head, diamond ear-studs and tattooed forearms, seemed to inspire - as it usually does - a certain foreboding among our fellow customers.
He had come to talk about Dying To Sing, his week-long series of concerts at the Twelve Bar Club, Tottenham Court Road, dedicated to the work of dead pop artists. But Croker, who is uninterviewable in any normal sense and appears bored by talking about his own work, was soon reminiscing about the problems currently besetting an impoverished earl who, he says, accompanies him on woodpigeon shoots at home in Yorkshire.
"As I told him," Croker boomed at one point, "what do you expect if you turn up outside the door of every woman's door on your estate, demanding droit de seigneur?"
The Twelve Bar project - at which Croker, with a varied supporting cast of musicians, will perform the work of dead stars including Kurt Cobain, Bob Marley and Vivian Stanshall - is a typically idiosyncratic scheme.
"It started from a conversation about the Little Feat singer Lowell George," he told me. "One of my friends said: `My God, don't you miss him, as a songwriter.' Then we got talking about Rick Nelson."
Nelson, Croker recalled, blew his own plane up, reportedly because he insisted on freebasing cocaine while the plane was landing.
"I'm fascinated by these people," he said, "as they made other people's lives better, often at the expense of their own."
Brendan Croker himself has made several magnificent records - notably Boat Trips in the Bay in the late Eighties, and the splendidly titled Redneck State of the Art in 1995. Shortly before that, he wrote What It Takes for the American country star Wynona Judd: it sold 4 million copies and earned Croker more than pounds 100,000. Then, just as he had established himself as a Nashville songwriter, collaborating with the legendary Chet Atkins, he apparently lost interest, and set off on an acoustic tour of Belgian prisons. It was a typical career move for the singer who has, I suggested, frustrated many supporters with his perverse indifference to success.
"Well I'm sorry I've been a disappointment to you William," sneered Croker. "I do believe I've had the potential to make big-selling records, but nobody's really known quite what to do with them."
Brendan Croker, who was born in Bradford and studied at the local college of art, was 30 when he started recording seriously. Before that, he had something of a chequered CV.
"I had jobs - I was a bin man and a railway guard," he said, "but I generally got fired for enjoying myself. Yorkshire Electricity Board - that was a good sacking."
He was painting scenery at Leeds Playhouse when he fell in with the virtuoso blues guitarist Steve Phillips, who taught both Croker and Mark Knopfler, and still performs with their occasional group, the Notting Hillbillies.
"One of the things I like about the band," said Croker, "is the way that it isn't overburdened with ambition. One of my favourite songs is the single by Johnny Paycheck: "Take This Job and Shove it: I Ain't Working Here No More".
What about his retreat from Nashville, just as things were taking off?
"I loved the innocence of the place at first," he said.
"Before it all turned into a cynical big business. I don't like what they are doing now, musically or socially, so I don't go there." Boredom, says Brendan Croker's associate Paul Crockford ("manager", in relation to Croker, is probably not a meaningful term) is a recurring problem.
"He gets tired of things," Crockford said. "He has always adhered to the principle of `don't do what you can do, do what you can't', and that's why he's so interesting. If he were richer," Crockford added, "he'd be eccentric, but he's poor, so he's mad."
Croker's live shows are always compelling, if only for his fondness for involving the audience - often with terrifying prominence - and his refreshingly unpretentious philosophy. Last year, at a Notting Hillbillies concert at Ronnie Scott's, Mark Knopfler, looking slightly out of place among his old Leeds pals in a hand-stitched grey silk shirt, introduced a number as: "One of my songs that just about everybody's recorded."
"OK," said a gruff Yorkshire voice at his elbow, "who's done it then? Dame Thora Hird? Archbishop Tutu?"
On stage or not, Croker is a man who knows no sense of shame.
"One of the worst moments of my life," says the journalist Mark Ellen, "was with Brendan Croker in a London pub, packed with city traders in red braces. He had a guitar case with him, and he said: `What's your favourite Woody Guthrie song?' I told him `Grand Coolie Dam'. He got to his feet, shushed these hundred bankers to silence, turned to me and bellowed: `Sing it man. Sing it now.'"
The stage backdrop at the Twelve Bar Club, Croker told me, will consist of Jon Langford's portrait of Hank Williams, pierced with arrows, in the pose of the martyred Saint Sebastian.
"I do slightly regret," said Croker, "that I can't do the odd song by people who are still alive. I don't wish any ill on anybody," he added. "That said, I am aware that a rock star's life is an uncertain business, and pavements can be slippy when wet. Late-comers will not be ruled out."
In the few months, Croker's entire back catalogue will be reissued, together with a "best of" compilation. Was he planning a new album, given that his last CD, Three Chord Love Songs, came out a couple of years ago?
"I've started to feel I've made too many records," he told me. "The next one I make, I want to die for every line I write."
His immediate plans after the London shows, he told me, are to spend some time in Leeds looking after his two carthorses.
"I think I like carthorses," he said, "because they don't do anything they don't want to do. That," Croker added, "is a good example for anyone."
Brendan Croker is playing the Twelve Bar Club, London. Booking: 0171- 323 3003Reuse content