Many comedians talk about ‘the spectrum’, but Will Duggan is surely the only one who means the band of electromagnetic radiation with wavelengths between 400 and 700nm, visible light. He does ten minutes on this, aided by an hilariously cheap hand-made visual aid, despite not being on the neurodiversity spectrum.

Funny as this obscure obsession is – mainly because of the ridiculous extent of his nerdy upset at the rainbow – it may not be the sort of material that will get him on Live At The Apollo. But at 37 and 15 years into a comedy career, Duggan is starting to accept that probably won’t happen now anyway. For although he loves comedy, and makes an OK living at it, he is beginning to reflect on whether he has fulfilled his potential in this, or in life.

Perhaps what’s triggered this is that he’s become a father, the sort of life-changing event that would get supportive hollers if revealed to an American audience, dead silence in Edinburgh.

Cue some relatively standard observational material about the unwelcome pressure to make friends in the ante-natal class and how easy dads have it compared to mums, taking some easy Brownie points for being so feminist for mentioning it. 

The anecdotal material switches between his hopes and desires that his daughter will fulfil her potential, and his frail father, bringing up the subject of euthanasia so brutally it’s funny.

Accomplished crowd work with one younger member of the audience – teasing her for not getting any of his references – playfully highlights cross-generational differences, even if Duggan, like most people, still considers himself young.

This a solidly funny hour – those 15 years means Duggan knows how to tell a story with confidence, rhythm and enough looseness to make it all feel conversational, while under the bonnet the show is more carefully put-together than it seems. 

Yet without the extra nugget that turns a good show into an excellent one, is Duggan living up to his full potential as a comic? Only he knows that…