There’s a scene in Eternal Beauty where Jane (Sally Hawkins) – a woman battling with paranoid schizophrenia – is mercilessly grilled by her self-obsessed younger sister Nicola (Billie Piper) on the “fucking weird stuff going on in her head”. This is no teary heartstring-pull of a familial confession. No tight camera angles and breathy cathartic sibling admissions. Nicola needs Jane to “show [her] some stuff” i.e. “the fucking weird stuff” so she can feign symptoms and claim benefits on a mental health condition. To a quizzical and startled Jane, Nicola wearily sighs: “There’s nothing wrong with me Jane, I’m normal”. Cut to the next scene and Jane is enthusiastically reassuring a concerned social worker that the exaggerated displays from Nicola mean “she’s very, very ill”. A worthy accomplice.

This pitch-black scene is one of the many acerbically humoured exchanges in the dark and distinctive second feature by director, writer and actor Craig Roberts. But don’t be fooled; Roberts is by no means poking fun. The humour means we rarely see Jane as a victim of her condition – with scenes also spliced with devastating flashbacks (Morfydd Clark plays a young Jane). Humour and humanity dizzily engulf each other in this risk-taking tilt-a-whirl that tackles mental health while resisting reductive and hackneyed tropes. For the viewer, laughter comes guiltily and reluctantly, and then in uncontrollable, belly-shaking guffaws. For Roberts – who based the character of Jane on someone he knew growing up – the laughter frames, punctuates and sets up the oft uncomfortable, yet emotionally riveting scenes. Artfully and empathetically, and with unabashed rigour from Roberts and the genius cast (Billie Piper is hilariously despicable), it is fortified how mental illness is something that requires resilience, power and inner strength.

We caught up with director Craig Roberts on how he settled on the name Eternal Beauty, and using humour as a tool to avoid the victimisation of mental health…

Hi Craig, how has lockdown been for you and impacted you personally and creatively?
Lockdown has been fine so far. Personally, it was at first terrifying because my mother is a key worker so it was very strange. But creatively, I thought I was going to have all this time to write but because the world is on fire I haven’t. It has been interesting and challenging at times I would say.

Congratulations on Eternal Beauty – what made you want to explore schizophrenia – which rarely receives appropriate or sensitive treatment on-screen?
Well, the movie is inspired by someone that I grew up with and was very close to me. I knew she had been living with this and I didn’t realise at the time how strong she had been while navigating through this. It just felt like I was at the right place and it was the right time to explore it and share this wonderful person with the world.

And why the name Eternal Beauty? Was there at any point another title you were choosing between? And what made you settle on this one?
The original title was In My Oils, which is a phrase in the movie, a Welsh saying that means “in your element”, but Eternal Beauty came to me because I saw this beautiful quote that said: “Eternal beauty could not exist if it were not for the face of a fatal flaw”.

I was also fascinated with photographs of people when they are younger and how people look at them and reflect on how they once looked, how all your photographs could be eternal beauty living forever. In the film, when Jane feels more comfortable with her present self, this is her eternal beauty, this is how she wants to be remembered.

How did your experience of writing and directing Eternal Beauty differ to that of Just Jim where you certainly have more experience and confidence under your belt now?
Well the two are completely different experiences. In one, I didn’t act in, which was a very good choice. For Just Jim, I was very new at directing and I had a lot of influences, it really felt like a diary entry. For Eternal Beauty, I had a lot more time to prep and discover my voice and what kind of filmmaker I wanted to be. Confidence is a strange thing with filmmaking, you have to show this front and be seen as confident the whole time. I don’t know if you are ever completely confident, you’re just more excited about the idea of something you will be proud of one day.

And the cast is absolutely sensational – did you have them all in mind from the start – and how did you feel when it was confirmed that they were attached? And Sally Hawkins as the lead…
Yes, I had all the cast in mind pretty much. I sent the script to Sally very early on, years before we actually made the film. She read it and said she wanted to do it which meant we had two years for prep. With Billie, Penelope and David, it felt like a competition really, we got them all! The fact that they were all game and very committed to what I intended to tell just made it a very enjoyable experience. They are all fantastic in it.

The film flits between comedy and tragedy, joy and cruelty – how hard was it to toe the line here, especially with such a sensitive subject?
It was very important for me to be humour in there. A lot of films that deal with mental health tend to be dark and treat the people as victims. This is about showing all the different shades of human beings. People are funny so why should we shy away from that, especially the person who inspired the film. She is incredibly funny and wicked at times. I just wanted to show every side of her. Sometimes when you put humour into such a heavy subject, people can feel uncomfortable and not know whether or not to laugh and that’s absolutely fine, it doesn’t mean that it is wrong.

What was the most challenging scene to film?
The most challenging scene to film was Jane discovering Mike with Nicola in her apartment. Sally had to break down and I felt so sorry for her that when we were filming, I could actually only do one take of it, I couldn’t do any more.

Stylistically were there any unusual places or films/music you pulled influences from?
It’s not an unusual place but Wales is certainly an influence because I’m from there. I just find the people fascinating and love how, although the film is not set in Wales, there will be a Welsh sensibility in it. Musically, I was very influenced by Paul Thomas Anderson’s Punch Drunk Love and Magnolia. Aimee Mann’s music in Magnolia just really helps the film with its nervy and kinetic feel and that’s something I was keen on using against the backdrop of a mundane UK.

What do you hope people take away from the film at its core? And what message on mental illness?
I just hope that people are really kind to one another and take the time to acknowledge that everyone has their own reality. It’s hard for me to send out a message on the umbrella of mental illness because I’m only talking about one person in here.

What’s the nicest or most unusual piece of feedback you’ve had so far on Eternal Beauty?
The nicest would be that it touched people and that people have a family member that it reminds them of. The most unusual feedback would be that people acknowledged that the water was murky in every cup which I didn’t think people would actually notice.

And for your next project – do you have any idea what themes/ideas you would like to pursue?
The next one is based on a true story and it’s about somebody not taking no for an answer and that you can be what you want to be really. I suppose the film is about hope.

Eternal Beauty is out 2 October in cinemas.