Hot Press was still recovering from a show the night before as he ambled into Vicar St at about 8 o’clock on Friday night, seeking liquid fortification. A cheer went up from the main room just as the bar was in sight, prompting a deep sigh as a heel was turned and a seat fumbled towards. Never has the promise of an acoustic night been welcomed with such open arms.

It’s only been four years since Sturgill Simpson’s self-released debut album, but thanks to his quite brilliant Metamodern Sounds In Country Music (2014), and the Grammy winning A Sailor’s Guide To Earth (2016), he now finds himself acclaimed as country music’s saviour. It’s a title that he roundly rejects; tonight he’ll put his success down to the “fact” that he’s really a CIA assassin, for how else can you explain an ex-military man becoming an award-winning singer in no time at all? The aforementioned records show an artist intent on escaping any particular pigeonholing; Waylon Jennings crossed with Otis Redding would only begin to describe him.

It’s Simpson’s voice that carries him tonight, a rich baritone that does indeed raise Waylon’s ghost on opener ‘Long White Line’, and again on ‘Time After All’ and ‘Oh Sarah’, but nowhere more so than on his cover of Willie Nelson’s ‘I’d Have To Be Crazy’- a song from the pen of the late Steven Fromholz, once the Poet Laureate of Texas, which beats everything else on LinkedIn, ever. Simpson indulges in several fine covers – Ralph Stanley, Jimmy Martin, Doc Watson - but it is his version of William Bell’s ‘You Don’t Miss Your Water’, as featured on Otis Redding’s Otis Blue, that is the most telling, with one foot in Nashville, and the other in Memphis. I very much look forward to the day he brings his full band show to these shores.

At one point, Simpson mentions how much he loves playing all around the UK, and Ireland in particular, prompting the crowd to howl at his geographical/political error. Some take it far more personally. Closing with a marvellous version of ‘The Promise’, after teasing us with a mention of ‘Turtles All The Way Down’, Simpson offers it as a “song for the ladies, as they all are”. This tempts a wiseacre behind me to “joke” how he’s sexist as well as racist (!). Perhaps we as a nation could offer a small bit of leeway here. Can you name the state capital of Kentucky? No? Neither can I. Ridiculous carry-on.

No less an authority than Bob Dylan once said, accurately, of John Prine that his “stuff is pure Proustian existentialism. Midwestern mind trips to the nth degree. And he writes beautiful songs.” A friend who saw him recently, for Simpson and Prine have been on a casual tour around the country, promised that Prine is on top form, as proves to be the case. Looking in rude health for a man who kicked the arse of two different forms of cancer, he opens with ‘Spanish Pipedream’, ‘Aimless Love’ and ‘The Glory of True Love’. Prine’s three man crew – himself, David Jacques on double and electric bass, and Jason Wilber who plays sympathetic guitar throughout, as well as a soulful harmonica solo during ‘Six O’Clock News’ – deliver a warm, soothing sound, welcomed by the crowd like a duvet after a long day.

The songs are a dream selection from across his career, with more than half of his lauded 1971 debut album getting an airing, including a gossamer delicate ‘Hello In There’, a stirring ‘Angel From Montgomery’, and a heartbreaking ‘Sam Stone’. The rest of the set is peppered with the highlights from a master’s songbook – ‘Fish And Whistle’, with it’s laughed-off fluffed verse, ‘Christmas In Prison’, ‘That’s The Way The World Goes Round’, ‘Blue Umbrella’, and a quietly bopping ‘Grandpa Was A Carpenter’, introduced with a funny if well worn gag about how he always wanted to grow up to be an old man. He dedicates ‘Your Flag Decal Won’t Get You Into Heaven Anymore’, a song he says he usually reserves for election years, to “our führer, Adolf Benito Trumpitini” to loud cheers, it is barrelled-fish shooting at its finest.

Simpson is back on stage to help out on ‘Please Don’t Bury Me’ and add a sturdy vocal to former Irish C&W National anthem ‘Speed Of The Sound Of Loneliness’, before giving way to the band who finish with a long belt of ‘Lake Marie’, a Dylan favourite apparently. It earns a deserved standing ovation. After a short break, everyone, including Prine’s young son, returns to the stage for ‘Pretty Good’ and a stirring, fiddle-lead ‘Paradise’. Prine Jnr takes a verse to roar of approval, completing a circle by singing a song his father wrote for his grandfather. The delighted crowd is loath to let them leave.

There is no denying that the ill health which nearly took Prine has affected his voice, now a deeper animal than the one that originally delivered those seventies classics, but if anything it adds even further gravitas to the moving and unashamedly grown up music we are lucky to get tonight.