The Downton star’s latest role casts him as a celebrated establishment figure – but one who may be harbouring a very dark secret.

Hugh Bonneville is the quintessential Englishman. Charming, genteel, slightly bumbling, he’s showcased our most endearing qualities to the world via global smashes Downton Abbey and the Paddington movies.

In his latest film, I Came By from director Babak Anvari, he plays Sir Hector Blake, a highly esteemed judge targeted by a graffiti artist (George MacKay) who breaks into his home to have a go at an establishment figure by tagging his sitting room wall.

“Hector Blake is a man who has stood up for the underdog,” Bonneville says. “He’s a pillar of the establishment. And thank goodness there are people like him to fly the flag for decency and honour.”

But there’s more to Hector Blake than meets the eye. People who intrude in Blake’s world quickly regret it, giving Bonneville the opportunity to express some serious rage in a violent, deliciously Hitchcockian thriller. But Bonneville tells us that he still sees his character as the hero.

The Big Issue: The poster and trailer of I Came By seem to suggest you might be playing a bad guy…

Hugh Bonneville: All trailers these days are designed to give away the entire plot. But that aside, it could be double bluffing. It’s actually a lightweight comedy and Netflix are just trying to draw you in by suggesting there might be some hidden secrets. But when you’ve got a lead actor like George MacKay or Percelle Ascott [who plays MacKay’s friend and sometime accomplice] really, the film is about them and I just dip in a bit.

The trailer may be bluffing but in it you say: “I really tried to be kind, but I had this rage that was so liberating, so empowering.” Did you find it liberating and empowering to have an outlet to express rage you may feel yourself?

I don’t feel rage in my real life. I feel dissatisfaction, I feel anger, like many people.

Do you want to play people that aren’t just cuddly?

Every actor likes to think they’re as versatile as an elastic band, we all think we can stretch in different directions, but on the whole we get pigeonholed. Casting directors and producers sometimes don’t have that imagination. So I was very pleased that Babak allowed me to twang the elastic.

So are you actively looking for roles that allow you to twang the elastic?

It’s just got to be a cracking story. When I was reading this, I was constantly surprised by each page I turned and that was riveting. I mean, there’s no comparison at all, but in the same way that when I first read Downton Abbey I wanted to know what happened next. And also the character is properly complex, let’s say, and that’s always attractive.

Were you surprised that you could be scary?

I’m not scary, I’m cuddly. I play decent people. That’s why I’m cast in these roles.

You’ve played lords and earls and people that live on expensive streets in London. It’s not believable that those people could have a dark side, right?

Absolutely. I mean, look at the great address of society, 10 Downing Street, nothing wrong there. Or you go to a doctor’s surgery like Dr Shipman’s. He was a terrifically respected GP. Or indeed, let’s face it, quite a lot of people with dog collars in the past. Without bashing people over the head, if I can use that phrase, I think Babak’s film questions who we trust and why we trust them in an interesting, film noir-ish and slightly uncomfortable way.

Why does privilege and entitlement prevent people from understanding how others see them or what might be wrong with their behaviour?

You can look at it from the oligarchs in Russia, from Putin to our own higher echelons of the establishment. Everyone always talks about the Westminster bubble. It’s this little privileged world, which finds it hard to understand that anyone would think differently, or indeed not think that it is as important as it thinks it is.

The rest of the country may be screaming out loud. We need to fix, let’s say, a fuel crisis, and they’re bickering about who’s wearing expensive earrings to a debate on who’s going to lead the country, [which is] voted on by 150,000 people. Something is skewed.

What is it we accept in society? What do we turn a blind eye to? What is the next step? What is the solution? And that’s where I think so many people find themselves disenfranchised. How do we make a difference?

Whose responsibility is it to make a difference, the people at the top or the bottom?

In theory it should be the democratic system invented by the Greeks two and a half thousand years ago. In Athens, third century BC, every decision of the city state was made by a forum of people discussing it and voting on it. So it should reside in the democratic system, but does it? That’s the big question. I don’t think that it does.

Hugh Bonneville as Hector Blake and Franc Ashman as DS Ella Lloyd (Photo: Nick Wall/Netflix)

Can a film like this – or art of any kind – actually make a difference?

Without sounding too airy-fairy, I think art in any form, be it music, be it dance, be it spray-painting on a railway arch, is an expression of our emotions, attitudes and expectations of the world. If a work of art of any sort moves you, shifts you on your emotional axis in a tiny way for a heartbeat, then it’s of value.

We sideline the arts, as the education system has done – and is doing – at our peril. Otherwise, we become functional beasts, rather than imaginative humans who can solve each other’s problems by empathy.

Do you have any plans to travel to Darkest Peru anytime soon?

Funnily enough after the second bear film, the cultural attaché of Peru did suggest a publicity tour. Or certainly extended a warm invitation to the Brown family. I haven’t been to South America. I’m dying to go. It’s on my bucket list. So maybe 2023 is the time.

Is there anything you can say about Paddington 3?

Well, only insofar as it’s a bit like trailers, they’ve now given away the entire plot. They’ve announced publicly that it’s called Paddington in Peru. So I think there’s a clue there. A visit to Aunt Lucy is probably in the offing.

Hopefully the Browns can go along?

I hope so. Maybe we’re stuck at home fixing the roof.

I Came By will be in select UK cinemas on 19 August and on Netflix from 31 August