Childhood sweethearts Peter Thorburn and Sheila Currie had reunited after she spotted her former flame in a television advert.
They decided to get married and planned a trip down the Thames ahead of their big day.
But their dream getaway turned into a nightmare when Sheila fell from their powerboat into the river and became trapped by its propellor.
Peter watched helplessly and held his fiancée’s hand while screaming desperately for help.
At first she seemed fine, but the dark water had masked the extent of her bleeding and Sheila died in his arms.
Speaking today to the Evening News, Peter, 70, said: “The boat trip was supposed to be a surprise for me. She was just like that.
“Sheila was a very adventurous person. I would wake up in the morning and not know where I was going to be for the rest of the day.”
The couple had decided to stop for lunch on the riverbank and were trying to moor the craft near the lock gates when Sheila slipped from the boat.
Peter said: “I was turning off the engine and I heard a yelp.
“It wasn’t a scream or anything so I didn’t realise at first anything was wrong.
“I couldn’t see her anywhere on the boat or the bank but then I saw her hanging on to the back of the boat. I thought she was just standing there as the water was quite shallow.
“I went to give her a lift out but I couldn’t move her as she was stuck.
“She just looked at me. I said, ‘Are you all right?’ and she said ‘Yes, just don’t let me go Peter’.
“She told me she couldn’t feel her leg and then her eyes just flickered and she was gone.”
The craft’s propellor had pierced her thigh and slashed a major artery, but the murkiness of the river concealed the fact the grandmother was quickly bleeding to death.
“I had been shouting for help, I was desperate. I couldn’t see what was wrong,” said Peter.
The lock keeper came to his aid and the pair were able to lift Sheila on to the bank, but it was clear to her fiancé that it was too late.
Paramedics desperately tried to administer treatment at the scene, but Sheila, 69, was taken to the John Radcliffe Hospital, in Oxford, where she was pronounced dead later that afternoon.
Devastated Peter could not understand what had happened, as Sheila was experienced on the water and had often been in similar crafts.
He said: “It was such a shock. It’s like something had been snatched away right from my very fingertips.
“I always thought I was quite strong but this was too much.
“She was going to be my wife. My son saw her as a mum, my whole family loved her dearly.”
Last week Peter had to endure attending an inquest into Sheila’s death in Oxfordshire, which brought back the pain he has tried so hard to bear.
He said: “I was just getting back on to a level and then it hit me all over again.”
The agony of her death was made worse by the fact that it took the couple decades to find each other, after losing touch more than 30 years before.
Peter was raised in Fountainbridge and trained as a blacksmith in the Old Town before downing his tools to become an actor, with roles in everything from bit parts in Taggart to American sitcom Two and a Half Men.
Sheila was born just outside Stirling and moved to Edinburgh for a job as a personal assistant with a computer firm, living with her young son Matt in a flat in Abbeyhill.
The pair first met at a cultural function at a West End hotel in the 1970s and fell in love.
They dated for two years until their jobs took them to different ends of the country and they lost touch.
Both Peter and Sheila went on to marry other people, with Sheila raising her son Matt and two grandchildren, who live in Canada, while Peter had a son, also called Peter, now 45.
But the pair never stopped loving each other, and began to search for one another when both of their marriages ended.
Peter moved to England permanently seven years ago to continue with his television work, before Sheila spotted him by chance in an advert and contacted his agent.
Peter, who now lives in London, said: “For years both of us had been looking for each other.
“Except I was looking for a Sheila Price, which was her maiden name, rather than Sheila Currie.
“From the day we met in 2013 at Waterloo Station, we were never apart again.
“It was like we had never been apart.”
The couple lived together in the village of Hartley Wintney, in Hampshire, for the last two years of Sheila’s life and had been due to marry on board a cruise ship last month.
Peter said: “I’ve never been in love like it in my life. We both knew that was just it for us.”
He added: “She was 69 years old but everyone thought she was 50. She was so young at heart.
“She was just a wonderful person.”
Family and friends packed out a celebration of Sheila’s life, which was held on June 5.
A coroner in Oxfordshire recorded a verdict of accidental death during an inquest into her death on September 30.