She was the man who became a father who learned to be a woman so she could be a mother. And Louisa Wall's marriage equality bill also made a big difference.
Day 9: Ellerslie, Auckland
This is a story about a boy called Finn.
To get to Finn, we have to start with another boy - the boy whose own story is much like an adventure tale.
It's the story of the boy who undertook a long and terrifying journey, beset by demons, to eventually become Finn's mother.
In those two years, Lex was often dressed as a girl with mum then as a boy for the times dad came home. "I was Sally or Susan. It was like she twigged on to something early on."
Lex was a voracious reader. Among everything she read was a story in the Australasian Post about Christine Jorgensen, the first widely reported case of gender reassignment.
"She was walking down the steps from a DC3 looking like Marilyn Monroe." The magazine went under Lex's mattress. "That was at the back of my mind for a long time."
It stayed at the back of Lex's mind for decades. It stayed and it agitated.
"I played rugby and cricket and did all the boys' stuff. I needed to prove this thing dangling away down here meant something. I became a truck driver, because that's what blokes do. I joined the army, because that's what blokes do. I drank a lot, because that's what blokes do."
Life was a masquerade, although an unwitting one. Lex was a teacher turned actor, the stage and set offering chances to wear different masks. As an actor, Lex was regarded for roles amplifying masculinity. "It was a role I'd been playing for 40 years." There were television roles in Hercules, Mercy Peak, Street Legal and countless stage parts. There was also the opportunity to cross-dress, part of an ongoing and largely unconscious search for identity. Lex wondered if sexuality lay at the root of the uncertainty but was attracted to women rather than men. There was promiscuity, as if the question to the answer was "will more sex help"?
"I was putting everybody at risk. I don't know what I was."
Life edged towards tipping point. Lex won a study award, travelling to the United States, Canada and Europe to study Shakespeare production and was staying at a backpacker hostel in Zurich when life, structured as it was, caved in. Lex, with long hair and a beard, stood naked in a bathroom walled in mirrors and knew life had to change.
Lex returned and sought counselling. Childhood sexual abuse was worked through and, while driving home one day, Lex realised life had been lived with freedom from suicidal thoughts for three months.
But the epiphany was still to come. At one therapy session, counsellor Wayne Gates set out two chairs. "Lex," he said, "you sit there and Sally will sit here," he gestured to an empty chair. Lex inhabited both and played both parts, moving from one chair and character to the other, talking and talking, and crying. "That was me sitting in that chair," said Lex to Wayne, pointing to the empty chair.
When Lex told his partner of 20 years that sex reassignment was coming, she responded saying: "That's that then."
"But why?" Lex asked. The response: "Because I'm not a lesbian."
Lex was, though - or would be once the gender reassignment was done.
First though, there was Cushla.
They met when Lex travelled to Wellington to produce a show for the 150th anniversary of the Catholic Archdiocese. They became friends, the 30-year age gap no barrier. Lex laid it all out - the struggle for identity, the lost years, the decision to become a woman.
Cushla listened, then asked: "Shall we have pizza for dinner?"
They married at St Patrick's Cathedral in Auckland. Barbie and Bob the Builder were on the wedding cake. There were plenty who assumed Lex was Bob the Builder and Cushla was Barbie but they had it the wrong way around. That would become clearer soon enough.
And this was about where Finn comes in. "We decided we would try for a child. At my age, I wasn't even sure it was possible. He's a wedding night baby - conceived on our wedding night." And then, having fathered Finn, Lex became Lexie.
The hormones and hospitals were only part of the journey. Lexie was buried under half a century of being male.
"A lot of gender is learned," she says. There were experimentations with dress, hair and other styles.
Lexie became involved in LGBT (lesbian, gay, bisexual, transgender) issues - "a lot of people become born again", she says of her "activist" years. It was, in a way, like the "Dolly Parton-dress phase". It was a search for herself.
It didn't all come easily. Cushla's conservative parents had triple shocks - their son-in-law turned out to be their daughter-in-law and then Cushla came out as lesbian. It was difficult. One breakthrough came while shopping one day when Cushla's mother pulled out a blouse she had bought and Lexie produced the same top. "Oh no, I've married my mother," Cushla exploded. There was also straight talking: "This is us. This is how we live our lives," Cushla explained.
And always there was Finn. "He calls me Mumsie," says Lexie.
When he was two-and-a-half, he decided he was a ninja. Lexie would go in to get him ready for kindy, asking: "How did you sleep?"
"I didn't sleep," he'd reply. "Ninjas don't sleep. They just rest their eyes."
Let's go with it, they decided, and took him along to martial arts lessons. Cushla: "We sat there for six months watching him." So she said to Lexie, "This looks like fun".
And it was, so now they all do it. As a family.
Finn, 11, currently holds New Zealand and Australian titles and has trained with grandmasters here, in Australia and the US. Cushla, 39, is New Zealand champ in two different styles.
Lexie, 68, who approached her first class worried about her knee replacement, says: "I compete. And do my best."
At karate, they met someone from Amnesty International about the time Louisa Wall's marriage equality bill was being debated. As a family, they had a contribution to make and testified before the select committee hearing submissions on the bill.
There was a lot of talk from opponents of the law that it wouldn't actually make a difference, so why change it. It was an easy counter-argument - if it isn't going to make a difference, why not change it.
In the Matheson household, it was going to make a significant and important difference.
For all the ground Lexie had covered on her journey to becoming a woman, her birth certificate still described her as male.
When the couple married, Lexie was Lex. The moment she changed her birth certificate to Lexie, a divorce would be required. The marriage would cease to exist because the law failed to recognise same-sex marriages.
"We had to make a decision. What's more important? Being married and having a birth certificate that said 'male' or becoming divorced and getting a new birth certificate?
"I made the decision because I love my family not to change my birth certificate." The law changed, equality won. The birth certificate change lies ahead. It is the final step in Lexie's journey.
It has taken an astonishingly long time to find her place in our world, but it is as one of two mothers of a beautiful young boy growing up in Auckland.
She was the man who became a father who learned to be a woman so she could be a mother.
"I actually found myself," she says.
"I don't know what I've done to pull all that together - but it has given me a life."
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Emergency services were called to the scene about 8.30pm.