THE best thing on telly at the moment? Line of Duty. Without a shadow of a doubt. The BBC drama is a hot topic of watercooler conversation for its whip smart writing, enthralling sub-plots and twisting storylines (not least last Sunday’s jaw-dropping cliffhanger).

There’s another reason it stands out. With TV shows increasingly dominated by privately-educated actors from affluent backgrounds – the Benedict Cumberbatches and Tom Hiddlestons of this world – the programme’s stellar lead actors Martin Compston and Vicky McClure are working-class heroes to be cherished.

It brings into sharp focus a debate simmering for some time – and set to reach boiling point – regarding what is dubbed the “class ceiling” within performing arts.

Why is there such a dearth of working-class actors on our screens? Alan Partridge star Steve Coogan has a theory: “It’s not enough being talented, these days you need cash.”

It is a sentiment that was echoed by Line of Duty actor McClure when I interviewed her earlier this year. She got her start with free classes at Bafta-winning drama group the Television Workshop in her hometown of Nottingham.

“I was accepted into Italia Conti [in London] when I was about 14,” she said. “The reason I couldn’t go was because we couldn’t get the money together because it was so expensive. Some people just don’t have the funds, but they have the talent. It seems unfair to me that people are penalised.”

Roles within the industry – whether on-screen or behind the scenes – are becoming more and more inaccessible for many people from less well-off backgrounds.

Julie Walters famously warned that we’ll see “middle-class people playing working-class people, like it used to be”. Michelle Collins, who played Cindy Beale in Eastenders, went one step further saying: “Julie was wrong – middle-class actors already do play working-class roles.”

Collins has recently given evidence to an inquiry into working class access to the performing arts being led by Labour MPs Gloria De Piero and Tracy Brabin, herself a former Coronation Street actor.

The inquiry, Acting Up: Breaking the Class Ceiling in the Performing Arts, will examine the “leaky pipeline” within the industry and aims to identify the stages at which working-class actors (and those in backstage, writing and directorial roles) slip through the cracks.

Submissions are being collated with a report to be published this summer. It should make for interesting reading, not least if it bolsters academic research which found that 73 per cent of actors came from the middle class, while only 27 per cent were working class.

The 1960s heralded a golden age for working-class actors with the rise of the kitchen-sink drama juxtaposed alongside increased social mobility and a wider cultural awakening. That has all but died away. The time is ripe for a second revolution.

Why is it vital to have visible and abundant working-class actors? Television within the arts is not merely about entertainment, but also has a duty to inform and comment on our society. It is irrevocably intertwined with our sense of identity. To dilute that is potentially catastrophic.