Five years ago, this acerbic singer-songwriter was transparently a major talent when, aged just 18, his debut album topped the UK chart and went on to go double-platinum. Inevitably, he was even hailed as the new Dylan. World domination appeared assured.

Half a decade down the line, Jake Bugg’s career trajectory is noticeably less spectacular. His record sales have slumped; there have been missteps. His third album, On My One, saw him unwisely dabbling in dance beats and even hip-hop. His latest, the country-hued Hearts That Strain, was recorded in Nashville with veteran studio musicians who backed Elvis and Wilson Pickett.

Such creative restlessness would usually be laudable, but in Bugg’s case the effect seems to have been to shear off the urgency and the rough edges that initially made him such a compelling artist. His new record is largely dreary, and nearly all of the highlights of this solo acoustic benefit show for Nordoff Robbins and Grenfell Tower fire victims are drawn from his first two albums.

Has he done too much, too young? There must be a downside to a life spent making an album a year and living on the road since his late teens. Where once he was all vim and brio, Bugg now cuts a world-weary figure, sighing his way through country-tinged songs of regret and reminiscence as if he has entered his twilight years at 23.

It’s a marked shift for a tyro performer who emerged snarling feral tales of a misspent youth watching drug dealings on a Nottingham council estate. Taciturn and black-clad beneath a tousled mop, Bugg remains fresh-faced but croons the languid, sparse Hearts That Strain and Southern Rain with the bruised fatalism of a grizzled resident of the Grand Ole Opry, or like Glen Campbell reincarnated.

It’s soporific and more than a little boring, and the night only comes alive when Bugg fires into the sprung rhythms and dextrous lexical gymnastics of his brilliant early roustabouts Trouble Town and There’s a Beast and We All Feed It. They embody the urgency the evening has lacked. An obvious message is reinforced by a provocative set-closing first-album triumvirate of Two Fingers, Broken and the 21st-century skiffle of Lightning Bolt. If Jake Bugg is to find his way, he needs to sound hungry again.

• At the Forum, Bath, on 4 November. Box office: 0844-888 9991. And touring.