Both still in their 20s, they had just bought a new home together, they had good jobs and were planning a wedding. And then everything collapsed.
"Mandy was a happy person, a phenomenal girl," says Tony, softly. "For the world to lose a person like her...it is a tragedy."
On November 24, 2009, on a quiet country road near her home in Stonehouse, 24-year-old research assistant Mandy took her own life.
Her death devastated her parents, Dougie and Sandra, and sister Vicki, and shocked everyone in the small South Lanarkshire town.
Mandy was beautiful and intelligent – she had been named psychology student of the year at Strathclyde University – and was well-liked by everyone who knew her.
"Mandy had been to the doctor not long before she died," explains Tony, 28, a banking services manager.
"Her auntie had died a few weeks before, and then her gran died, and she was very close to both.
"She had been to the doctor because she knew she needed help. She wasn't herself – she couldn't concentrate on anything for more than five minutes.
"She had been given anti-depressants, and had maybe taken four or five of them...but within a few days she was gone."
He adds, helplessly: "You always blame yourself, you always think 'There must have been something I could have done....'
His voice trails off. "Mandy had been diagnosed with depression before – about five years previously she tried to take her own life.
"But she had been given the right help, and she got better. This time, it was too late."
Since Mandy's death, Tony and Vicki and their families and friends have been fundraising for Action on Depression, a campaigning charity which helps people affected by the disease.
"It started at the funeral, really. Mandy's parents asked people to donate to the charity instead of sending flowers, and it grew from there," explains Tony.
"Afterwards, we decided to keep it going, because so little is known and understood about young people and depression that we wanted to help raise awareness.
"We set ourselves a target of £500, but that was beaten within hours – people have been so generous, and we're very grateful."
In fact, the Supermandy fund has now raised a staggering £35,000.
The young woman's friends have cycled round Millport, sung at karaoke events, climbed mountains and organised race nights.
Action on Depression has used some of the money to bring its highly regarded Look OK, Feel Crap campaign, aimed at young adults, to South Lanarkshire.
Gie's a Giggle, Tony's comedy night with the stars at Glasgow University's Queen Margaret Union on March 24, is the latest ambitious project.
"I used to do stand-up, but when Mandy died – well, there didn't seem to be too much to laugh about," explains Tony.
"But now, I think I'm ready to do it again, and I've had some fantastic support from Lewis McKenzie, who is organising the gig and comedian Billy Kirkwood who is compering the night."
The line-up is a secret, but will feature some big-name comedians appearing in Glasgow during the festival which runs from March 15 to April 1.
"It will be a great night –Mandy would have loved it," smiles Tony, who admits that throwing all his energy into fundraising has helped him to cope through the past two years.
"I suppose it has been a little bit about seeking redemption, in a strange kind of way.
"Of being able to do something, because I could do nothing to help Mandy in the end. I don't know. We talk to so many people through the charity now, and they all say the same thing. "If only we could have helped, if only we could have done more...."
Tony recently became engaged to his girlfriend Danielle Boan, who was friends with Mandy at university, and they have bought a new home together in East Kilbride.
"Danielle is an angel," he says, his voice breaking with emotion. "It has been tough for us both, and that brought us closer together."
And the couple, supported by Mandy's family and friends, remain dedicated to raising money for the Supermandy fund.
"We'll keep going," nods Tony, as he shows off the cartoon cow design, which has become the fund's mascot on wristbands, posters and badges.
"Mandy loved cow patterns and pictures – she had them on car seats, cushions, you name it!"
He adds: "Hopefully, we can keep raising money, keep raising awareness and if can we save even one life, it will have been worth it."
IT IS more than two years since part-time comedian Tony Goodall felt like standing up on stage and making people laugh. But next month he makes his comeback in a star-packed show in Glasgow's International Comedy Festival. Gie's a Giggle, featuring a host of well-known faces, is a gig with a difference. Its aim is to raise money for Action on Depression – and it is Tony's tribute to his fiancee Mandy, who killed herself in 2009 following a battle with the illness.
Tony tells ANN FOTHERINGHAM his story
n Gie's a Giggle takes place at the QMU on March 24. Tickets cost £13 plus booking fee from TicketScotland (www.tickets-scotland.com).
n To donate to the Supermandy fund, visit www.justgiving.com/supermandy.
n For more information about depression, visit Action on Depression's website www.actionondepression.org
n For information about the Comedy Festival go to www.glasgowcomedyfestival.com