Many gay men and women end up marrying people of the opposite sex. But what is it like for the spouse who eventually finds their marriage breaking down?
Recently we told the stories of gay men who had married women. It prompted a strong response from readers who had experienced it from the other side - those whose wives and husbands had come out as gay.
"It feels almost homophobic to say anything about them. To me it's not brave to spend 10 or 20 years with someone only to destroy and discard them," says Emma. She found out her husband was gay a year ago.
"They may go on and have a wonderful new life while leaving a crushed wife behind. You just feel like your whole life is wasted and there's no closure."
One of the most difficult things for many spouses is watching their former partner being celebrated as brave for coming out, but knowing the damage they've left behind.
It is an experience to which Carol, 43, can relate. With her former husband now active in gay rights, she received a message calling him an inspiration and a role model.
"I was disgusted by this, that someone actually considered him to be both of these things when he had spent our entire relationship lying to both himself and myself.
"To me, there is nothing to be proud of - he destroyed our family through his failure to admit that he was in fact gay," she explains.
They had married in 2003 and have two children - she says she was "very happy and in love".
But there were signs something wasn't right, including gay dating profiles on his computer, which he explained away. In 2009 he said he was bisexual but wanted to be with her.
Carol admits she was probably in denial but thought they would find a way through it as he was the man with whom she wanted to spend her life.
A year later it came to a head when he came home, said he was gay, and left.
"I thought my whole world had fallen apart but then he came back and said let's stay together for the sake of the kids. I didn't know what to do so we lived a lie for two years. To anyone else we looked like a normal happy couple," she said.
But it didn't work and they divorced.
Carol says the difficulty was the shock - he'd had time to get used to it but for her it happened so quickly. He's now married to a man and she says they get on for the sake of their children.
"It took me a long time to get over it, for me it is a trust issue. How can I trust anyone again? I can't compete with other men, I'm a woman, but he should have been truthful from the start.
"It would have been easier if it had been a woman - at least he would have loved me in the first place. He says he loved me but I don't believe him."
Kevin, 51, had been with his wife for seven years when she asked if he'd mind living in the spare room while she had a female partner. He'd had no idea she was gay.
"One day, she came to me and said: 'Is it OK if I had a girlfriend?'
"If a partner has an affair with the opposite sex you can be angry but this is so much more complicated. She'd been feeling like this for two years but said nothing," he says.
She wanted to remain married, but he couldn't live a lie and they divorced. They haven't spoken since and she now has a female partner.
Kevin's life fell apart and he became suicidal.
"I wanted to make a go of my marriage, I had everything invested in it, I didn't want to be a failure. I felt a failure as a man and a husband. It was bad, very, very, bad."
There are all kinds of reasons why people commit to straight relationships when they are gay - they may not have fully realised their feelings, hope they will go away or fear they will suffer prejudice. Some may have been together for years after marrying at a time when society was less accepting of gay people.
Former Welsh rugby player Gareth Thomas has talked about how he doesn't believe he would have reached the top in the sport if he had been openly gay. When he came out in 2009 he said he had been in denial about his true feelings and had genuinely been in love with his wife.
Both Carol and Kevin have a clear message for those who are in straight marriages but think they may be gay.
"You have to be honest with yourself and your partner, especially when kids are involved. Not knowing your own sexuality and taking time to decide hurts everyone involved. Be true to who you are," says Carol.
Kevin adds: "The sooner you come out the better for everyone concerned. It might be difficult, it might end a marriage, but the fact is you can't start to repair while they're in the closet but you're nailed to the outside and don't even know it."
Six years on, he describes his life as "brilliant" and now supports people going through the same experience. He says people in his position should contact the support group Straight Partners Anonymous.
"It will get better. It's been difficult, my life has now taken a completely different path, but is better than I could have ever hoped," he says.
Some names have been changed. Straight Partners Anonymous can be contacted at firstname.lastname@example.org
The Victoria Derbyshire programme is broadcast on weekdays between 09:15-11:00 BST on BBC Two and BBC News Channel.
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