With its 2014 adaptation of Jamaica Inn, the BBC introduced a hot new trend: mumblecore meets costume drama. The outfits on Jamaica Inn looked spiffing, as did the Regency Cornwall setting. But it was all for nought as it was impossible to work out what anyone was saying. (Similar charges were levelled at crime drama Happy Valley.) Such was the outcry around mumbling in many of the broadcaster’s dramas, BBC boss Tony Hall felt the need to intervene – setting out what was tantamount to a mission statement against mumbling (in 2013, a full 12 months before Jamaica Inn): “Muttering can be testing [when viewers find they] have missed a line … you have to remember that you have an audience.”

Things have not improved in the years since. And it’s hard not to think that Hardy, one of the pre-eminent Method actors of his generation, has given legitimacy to the idea of pitching your voice at a level that requires the audience to read the subtitles.

The contrast between today’s muddy dialogue and the whip-smart repartee of classic tinseltown is scalpel-sharp. On social media recently a blooper reel culled from the Golden Age of Hollywood has been doing the rounds. “Oh you’re following me?” says Jimmy Stewart as he notices the camera tracking him as he walks out of frame. He makes this observation with a zinging acuteness as if swapping banter with James Bond at the roulette table.

The blooper film is fascinating because it shows that, even speaking off the cuff, the stars of Old Hollywood knew how to deliver a line. “Goddamn,” says Barbara Stanwyck in another blooper – and she conveys more in that aside than Tom Hardy did in all of his screen time in The Dark Knight Rises.

It wasn’t just 1940s Hollywood studio starlets who understood the importance of clear diction. Actors in the UK were trained in Received Pronunciation, and with good reason. With most initially plying their trade in regional theatre, it was essential that everyone, in every corner of the theatre, understand what they were saying. Only as we have become more wary of cut-glass vowels has mumbling supplanted Received Pronunciation.

As is often the case with unwelcome fads, things are likely to get worse before they get better. Colin Farrell’s late career has been a cornucopia of crawing into his cuffs – whether in True Detective or last year’s The North Water, in which, as seal-hunter from Dublin, he sounded like a Fontaines DC B-side played backwards. And what of pre-cancelled Johnny Depp, whose Captain Jack Sparrow corkscrewed from decent Keith Richards impersonation to ghastly gibbering and grousing?