Comedian, actor and impressionist Phil Cornwell is a familiar face (and voice) thanks to his work on Spitting Image, Dead Ringers and cult sitcom Stella Street. In this Fringe show, he plays 'altered ego' Robert Lemon Alackadaddy, a booze-soaked sad sack battling demons from his past and voices in his head. It's not a million miles away from his wonderfully pathetic Alan Partridge character, DJ Dave Clifton.

From the start, Cornwell's crowd are unmistakably unsure about Alackaddady, a creation whose freewheeling thoughts enter the world without profundity or humour. 'We are all in this together,' he warns, although it's never certain where we're meant to be or why. While swigging from a vodka bottle, he recounts his fantasy encounters with Isambard Kingdom Brunel, Alexander Graham Bell and Alan Titchmarsh, as nary a snigger punctures the void. Walk-outs become so numerous that he weaves them into the narrative. For a time, it seems that a twist might be about to turn things around and make sense of this nonsense. But it never comes.

'You've gotta laugh, ain't ya,' he says with thundering irony as the audience loudly disagree through abject silence. On TV, Cornwell is a brilliant and funny performer but Alackaddady is way beneath his talent.

Underbelly Bristo Square, until 26 Aug (not 12), 4.15pm, £11–£12 (£10–£11).