A couple who underwent a life-saving operation last week are celebrating their engagement this Valentine's day after discovering they are a one in a million match.

When she found out her partner Melvyn Mather, 50, desperately needed a kidney transplant, devoted Dawn Hillier, 43, insisted he have one of hers. Doctors, who had warned the couple from Purley the chances of Dawn's kidney being compatible with Mel's body were a million to one, were astounded when the tests showed they were a perfect match.

Overwhelmed by Dawn's incredible act of selflessness, Mel decided propose to her on Valentine's Day. But last Wednesday, as they were both coming around from the life-saving operation, he was so relieved she was alright, he asked her to marry him.

Dawn, who works for the National Cancer Action Team at the NHS, said she never once doubted her decision to give Mel such a vital organ after they discovered they were a match in November last year.

She said: "The only time I started to worry about it was when I was in the anaesthetic room. I got a bit emotional. They let Mel come in with me and he was there looking after me."

Seeing Dawn looking so vulnerable upset Mel, but it strengthened his resolve to propose to her if they both managed to make it through the operation.

He said: "It was a gamble that we were both going to be in the recovery room at the same time, but our beds ended up facing eachother."

Dawn awoke just 10 minutes before they wheeled Mel into the recovery ward after his operation.

She said: "He was shouting, 'Where is my Dawn? Is she alright?' When I called to him and said: 'I am here,' he shouted, 'Will you marry me?'"

Mel had to repeat the question as Dawn was too astounded to speak. Unable to believe her ears, she asked the nurse looking after her what Mel had said.

"The nurse just smiled and said, 'I think he just asked you to marry him.' I said yes of course. It was just so romantic.

"My family were a bit shocked but they knew I was making a big commitment to Mel by giving him one of my kidneys, this is his big commitment to me. They are really happy for us, they know how in love we are."

The devoted couple met in July 2010 at an event at the OXO Tower in London. After a whirlwind romance, they moved in together in November, just as Mel's condition began to deteriorate. He had been undergoing dialysis for more than a year, both of his kidneys were failing and he needed an urgent transplant.

Dawn said: "I just knew I would be a match. Doctors told us it was very rare but I was convinced I would be able to give him a kidney."

The tests revealed that both Dawn and her 22-year-old daughter Heather were a match for Mel, as were some members of his family.

The couple were sent to specialists at St Helier Hospital and the "amazing" transplant co-ordinator Christina Ho managed to get Mel on the transplant list very quickly. Just 10 weeks after finding his match, Mel and Dawn were wheeled into the operating theatre.

Dawn said: "Everyone keeps telling me I have done this incredible thing, but for me it was an obvious decision, I love Mel and I would do anything for him. We are now looking forward to our future together."

Mel, a technical manager for a manufacturing corporation, said: "I just love Dawn to death, I can't thank her enough for what she has done for me, she has given me my life back. I will always have a piece of her with me, wherever I go."

The father to 23-year-old Lee and 19-year-old Rebecca is doing so well that doctors expect to discharge him today so he can spend Valentine's Day with his new fiancee. Dawn was discharged from hospital on Saturday.

They plan to get married in the Maldives in a year's time when Mel is well enough to travel.

The couple said they were incredibly grateful to the wonderful doctors and nurses at St Helier and St Georges hospitals who looked after them.

They have vowed to do everything they can to raise awareness about organ donation.

Dawn said: "I want to encourage other people to sign up to the donor registration list. A lot of people don't realise you don't have to die to be a donor. We have met people who have been given kidney's by perfect strangers who happen to be a match. There are 8000 people who are in need of a kidney transplant, if you sign up you could help save someone's life."

Mr Jiri Fronek, consultant transplant surgeon, carried out the operation.

He was delighted to hear of the couple’s engagement after the operation, and said: “Kidney transplantation from a live donor is the best therapy for most people with end stage kidney failure.

"We would encourage those who know people with kidney failure to consider being assessed for kidney donation - with modern medicines, kidney donors need not be related to each other.

"Last year the renal unit at St George's Hospital performed 100 kidney transplants and 60 of these were from live donors.”