Last Sunday I was working, so my husband Steve decided he’d put up a pair of new curtains. Except, first, he wanted to get the laundry done, so he began to sort through it – but then he remembered the shed was a mess, so he was knee-deep in old bicycles when he thought how much he wanted a pinboard where his tools could be stored in an aesthetically pleasing way.

By the time I returned at the end of the day, he was out picking up two of our teenagers, who he had forgotten about, dinner was still a pile of ingredients, and the curtains were in a heap on the floor.

This is the sort of disarray that used to make my teeth grind. There was no job too small for Steve to abandon halfway through. He would flit from one thing to the next, while I trailed behind him, putting things back in cupboards, sorting out the kids and finding his lost things: keys, spectacles, phone, dog lead.

My frustration would spill out of me into a big argument. Steve couldn’t understand my response because he didn’t see the path of unfinished jobs. He was already on to the next thing. I had three children, but it felt like I was responsible for four. It was a lonely place to be. Until finally one bleak January morning, after 20 years of navigating Steve’s unpredictability and impulsiveness, along with his regular mental health battles, I couldn’t take it any more.

While we had talked about separating at various points in our marriage, this time it felt different –and it needed one or both of us to be brave and call it quits. Which we did, mutually and sadly, exhausted by the turmoil that had temporarily drowned out the wonderful memories.

This was my chance to escape; to talk to our teenagers, get the estate agent round and work out a custody plan for the golden retriever. But I looked at Steve, who was in tears and utterly beaten, and I stalled. So I suggested that, before we took any further steps, Steve – then 55 – should make another appointment with the GP.

I had no idea this would start a chain of events that would lead to the discovery that ultimately saved our marriage: Steve has ADHD and autism.

Steve and I got together 23 years ago, when I was 31 and he was 35. I was a theatrical agent in a top London agency and disillusioned after a string of unsuitable commitment-phobic boyfriends. Steve was getting back on track following a difficult divorce and had recently embarked on a career change in building design.

Steve and Lucy got together in their 30s when she was a theatrical agent and he'd started a new career in building design

He was clever, funny, impulsive and prone to hyper-focus. I knew he was complicated – but I wasn’t, so it seemed like a good combination.

Our early relationship moved fast, our excitement occasionally tinged with angst and doubt. Steve regularly struggled with mood swings, low confidence and depression that would envelop him in a heavy blanket of inertia.

He’d been in therapy in an unsuccessful attempt to get to the bottom of this. I wish I could say I understood but I didn’t, even though I pretended to. I suppressed my fear and frustration, hoping more therapy would be the answer.

The good times overshadowed the bad, so we managed to keep hold of each other. Besides, we were old enough to know that fairytales didn’t exist. We were overjoyed when we had our first child when I was 34. I went back to work very soon after giving birth. Steve became a stay-at-home dad, while I was the breadwinner, and for a couple of years we pottered along, both of us happy in our designated positions.

Until we weren’t. I wasn’t the mother I wanted to be and Steve was keen to keep a foot in a working environment. By this point we’d got married. In a move I am still surprised by 20 years later, we left London, moving to Dorset. I resigned from my job, we sold our house and waved goodbye to our family, friends and healthy bank balance.

Steve and I had two more children and the years flashed by in a succession of beach picnics, primary school, financial jeopardy, house renovations and bedtime stories.

During this time, for no obvious reason, Steve’s mental health would take a dive. This could last for a few days or a few weeks; it could stop him getting out of bed or trap him in his office until midnight.

During these times I was bereft. I felt like I had lost my partner and gained additional responsibility I hadn’t signed up for. My main focus was the children and maintaining a happy equilibrium for them.

I knew he was complicated – but I wasn’t, so it seemed like a good combination, says Lucy

Money was a real worry as both Steve and I were freelancers. As much as I wanted to run from the difficult times, Steve was just as desperate to escape. Every time I felt I couldn’t take it any more, I saw how hard he was fighting. I didn’t want him to do that alone.

In hindsight, so much of what Steve dealt with was ADHD and autism-related, but we assumed his social anxiety, hyper-focus, distraction, time blindness, info dumping and difficulty managing his emotions were triggered by depression. This had been the story for most of his life.

There were instances where we’d argue about whether Steve could be different, and he’d tell me to leave him and find someone who wasn’t such hard work. I’d say that maybe I was exacerbating the problem, and he’d be better off without me.

We chased the subject around so many times, often after a particular incident that left him exhausted and me in despair, always reaching the same conclusion. To try again. To understand each other better.

While we didn’t want to put the children or ourselves through the emotional and financial upheaval of a break-up, there was something undefinable that stopped us. We were still working out the puzzle.

Which brings us back to that cold winter morning a couple of years ago, when we sat opposite each other to discuss a divorce, and this time it felt final.

Steve had been low for much of December, with a brief flurry of cheer over Christmas, before we limped into January. I couldn’t go through another year like the one we had just had, and Steve agreed. He said he didn’t want to be with himself, so why would I, and he didn’t want to put me through it any longer.

He’d given me his blessing to leave, but it felt like I was on a life raft, and he was standing on a sinking ship. So I suggested he make another appointment with the GP before we went any further.

In hindsight, says Lucy, so much of what Steve dealt with was ADHD and autism-related

Then, a few days later, I was updating one of my closest friends and she asked if Steve had ever been tested for ADHD.

The following day she sent us a book about neurodivergence; it was as if somebody had turned a light on. Inattentiveness, disorganisation, social awkwardness, a lack self-control; here were Steve’s traits.

The possibility illuminated the dark corners of our relationship and provided a framework for Steve’s behaviour. His depression was often triggered by anger with himself, the feeling he wasn’t ‘normal’. He immediately recognised himself on the page.

Armed with a self-diagnosis, Steve went to the GP. After spending his life battling something he couldn’t see or understand, he finally had a lifeline – except the waiting list for an assessment was at least two years. We felt he had no choice but to seek a private diagnosis – and were given the answer we had hoped for. I know hope is an odd word to use, but it was a relief to have an explanation.

Steve was prescribed medication and we waited and watched. The pills enabled him to be more focused, balanced his mood and boosted his productivity. He said they calmed the chaos in his head. I felt tentatively optimistic as he was happier, less irritated by the small things.

I could raise an issue without worrying this might provoke anger or upset.

Except there was something still niggling at him.

Lucy said they pushed their marital issues to one side and focused on Steve adapting to the revelations

It was an appointment with an NHS psychiatrist that provided the final piece of the jigsaw. After further in-depth assessments, Steve had a confirmed diagnosis of ADHD along with an additional diagnosis of ASD, Autism Spectrum Disorder. We were not expecting this, but it made complete sense to me, explaining the complexities and contradictions of Steve’s behaviour.

The dual diagnosis floored Steve. He’d accepted ADHD; there were pills for that and he’d worked out how to operate within those parameters. As for autism, there was no medication, it was about understanding himself better, putting coping strategies in place and having family support. Steve fought the autistic label for several months, railing against the preconceptions that can come with it, feeling shame. His acceptance was gradual and begrudging – and my patience was worn thin to transparent.

ADHD and ASD combined is a double whammy of difficult because they can fight with each other, requiring different things, which will send Steve into a tailspin. He can be exuberant and mischievous, yet also needs structure and familiarity.

He struggles in social situations, but is deeply curious about people and the world. There are sensory issues with sticky hands and loud music, unless it is house music, which he plays at full volume, finding the mind-altering beat calming. He can be overwhelmed by small everyday situations but is calm in a big crisis.

During this time our relationship was still fragile. We did not row back from the discussion about divorce, but neither did we actively progress it. We pushed our marital issues to one side and focused on Steve adapting to the revelations. We were kind to each other, we listened, and we learned more about neurodivergence.

It was liberating to hold this knowledge and apply it to every day annoyances, like punctuality, where I will tell Steve an earlier time to the actual one. Or being invited to a party, which I will now go to on my own rather than persuading Steve to come, thus avoiding anxiety for us both.

Now, when he moves around the house unravelling things, I walk him back through the chaos and we actually laugh about it.

I realised I’d suppressed anger towards Steve in recent years, keeping up the pretence of an always-happy marriage. Now, we spoke about these feelings openly.

But the one thing that still felt impossible to discuss was our future, because what if we didn’t have one together?

Throughout this year of discovery we both needed a distraction, something to keep us connected. The garden has always been Steve’s sanctuary and so we devised a plan for a veg patch and set up an honesty box selling the glut of our home-grown produce for a fee of the passer-by’s choosing. The irony of an honesty box at a time where we were finally getting to the truth of things was not lost on us.

I began writing about our experience – keeping a journal helped me to process. When I tried to find a book that spoke directly to me, written for people who support those going through a mental health crisis and neurodivergent diagnosis, I couldn’t find anything, so I decided to turn my diary into something I could share publicly.

Steve, who is the most courageous person I know, encouraged me to tell our story in all its good, bad, ugly and funny glory in my book, The Honesty Box. We’ve been overwhelmed by the number of readers who’ve contacted us to say our story is their story.

Today, several years later, we are still married. While the diagnosis has been life-changing, it doesn’t turn us into different people, but we have a better understanding of what we deal with. We have no idea what will happen next, but we are facing it together. I guess that is a happy ending of sorts.

The Honesty Box by Lucy Brazier (£16.99, Bloomsbury) is out now