In “The A Word,” Sundance TV’s poignant England-set drama focused on a family dealing with the diagnosis of their young son, Joe, with autism spectrum disorder, Lee Ingleby plays Paul Hughes, a father grappling with how to accept his son’s special needs while also celebrating his individuality and gentle spirit.

“When I was 19 I played a guy who had Asperger’s — he was obsessed with photography– but that was my only kind of interaction with autism spectrum disorder before doing the series,” says Ingleby, who since joining the series has become an ambassador for the National Autistic Society, a charity-based support group based in the UK. “I didn’t know anybody that had any form of autism or that was on the spectrum in any way. Now I work with a couple of actors that have autism on ‘The A Word,’ in various different ways, so that’s my way in toward understanding the disorder.”

Based on the original Israeli series “Yellow Peppers,” “The A Word” is one of several shows dealing with autism — “Atypical” and “The Good Doctor” are two others — but it’s also the most thorough and elucidating in terms of capturing how the disorder affects the familial unit, what challenges and disruptions it presents and how difficult it can be to do what’s best for one’s child when faced with so many different, and often confusing, therapeutic paths.

“It was all down in the script. It was so brilliantly written — they wanted to get across the fact that parents think they know their child the best, and what is best for that child,” says Ingleby. “The mother had thought one thing was best for her child, and the father thought something else was best for the child, and the exterior family knew that they were both wrong. Paul isn’t right in many ways and yet he is fueled by love and also discomfort and confusion and being scared of what it all means.”

Set against the backdrop of the bucolic, verdant hills of England’s Lake District, the Hughes family erupts into domestic chaos. It’s a stark dichotomy that works brilliantly to illustrate the emotional chasm that can exist between an autistic child and the people trying to understand and help him: everybody sees the world differently. Joe, played by the precociously gifted Max Vento, is fixated on music (Julian Cope’s anthemic 1987 track “World Shut Your Mouth” plays throughout season one) and solo morning walks. He also possesses the behavioral rigidity that’s a signature earmark of autism. Joe’s mother, Alison (Morven Christie), on the other hand, is beside herself with worry and devolves into a control freak, arranging a de facto homeschool plan that goes almost comically awry and raises the anxiety level of everyone in the family. To wit, in season one, Christopher Eccleston, who plays Joe’s grandfather, is at such a loss for how to handle the five-year-old that he winds up taking him to a bar. And Alison is apoplectic.

“Alison becomes sort of obsessive, like a bull in a china shop,” says Ingleby. “She doesn’t really consider her actions. It’s upsetting to not only her child but to everybody around her. And now [Paul] has started to lose his grip, too, because he’s seeing the future for the first time and he doesn’t like what he’s seeing. And it just feels like he’s slowly losing his boy.”

While he has no first-hand experience parenting an autistic child, to immerse himself into his role, Ingleby “goes down the route of imaging what would I do in this situation.”

“You’ve got to remind yourself that actually it’s not you that’s being presented on screen–it’s a certain character from a certain background and a certain social class. And with the dialogue that you are given and the scenes that you are doing and the history of the character that’s been decided, then you’ve got to decide what would this person do, not what would I do. It’s fascinating because some of the things you say you would never do– whether the intention was right or wrong– is what your character winds up doing. So, you’ve got to overcome your own personal feelings. And even though these character have their dysfunctions and they are lacking communication with each other, it’s all borne out of love at the end of the day.”

That in real life Max is not autistic, and plays Joe so convincingly, is one of the series’ myriad laudable strengths, notes Ingleby.

“He’s a very intelligent kid,” he says of Vento. “He knows Joe well enough now to know that when action is called the thing to avoid is eye contact, to avoid any responsive actions and gestures, and to just to be in his Joe bubble. He becomes Joe. He spends a lot of time in his trailer listening to music. But the main thing is that we spend a lot of time talking to Max in his scenes about what he needs to do. He’s a real bundle of energy and he has to remind himself during the takes that he has to be quite still.”

Whereas the first season of “The A Word” was primarily about Joe’s diagnosis and its immediate aftermath — and the denial that comes with it — the second season is focused more on acceptance.

“We try to shape our lives when actually what we need to do is to shape ourselves around Joe,” says Ingleby, who next up appears in the animated series “Watership Down” and the TV miniseries “Innocent.”

“Ultimately, the show is about difference,” Ingleby says. “It’s about not pushing somebody into something they don’t want to be because it makes the rest of us feel better and safe and comfortable. It’s about raising awareness, because it is confusing and nobody does really know what it is, even if you do know what it is. And, actually, maybe that autistic child isn’t odd or badly behaved–maybe there’s something more.”