It was an ordinary night in March, 1972, when Tasmanian couple Katy and John Woodroffe were walking towards the Tube station in London's busy Oxford Street.

One minute they were navigating the peak-hour footpath, the next they were on the ground and John was fighting for his life.

"I was waiting for Katy and then we met up, started chatting about cricket and this explosion occurred ... it's the only way we can think of it," John said.

"I was obviously KOd and knew nothing more."

The couple had been struck by a pregnant woman who jumped from the fifth floor of an office building.

Remarkably, the woman and her unborn baby survived.

But John was in a bad way.

Katy still remembers the moments after they were hit.

"I looked over and John was slumped against the wall, not looking good ... it was just awful to see him like that," she said.

"I didn't know anything about what had happened, I had just presumed it was an IRA [Irish Republican Army] bomb."

The Woodroffes and the pregnant woman were rushed to London's Middlesex Hospital, where John's injuries were found to be extensive.

In one moment, he had gone from walking down a busy street to having both bones in his left leg badly broken, his collarbone fractured and some vertebrae and ribs cracked.

Surgeon Sir Bernard Riberio (second from left), with John and Katy (right). ( Supplied: John and Katy Woodroffe )

"My head was fine, thank God!" he said.

But the worst was still to come.

Not long after John was admitted to hospital he experienced a complication — a rare fat embolism syndrome — which changed his condition to critical.

The embolism is a condition that can be associated with respiratory failure when severe.

"I remember him being very touch and go for a long time," Katy said.

John was returning to Australia in very different shape than when he left. ( Supplied: John and Katy Woodroffe )

John's surgeon at the time, Bernard Francisco Ribeiro (the Lord Ribeiro CBE), said it was one of the rarest cases he had ever seen.

"This particular injury he had is quite a rare one, and he was obviously quite traumatised at the time," Lord Ribeiro said.

"It was quite devastating."

John took weeks to recover from the embolism, meaning his other injuries struggled to heal.

Medical staff at the time said it was unusual to fully recover from such a complication.

"I remember getting back into the main ward after seven weeks, and the doctor said my leg had not healed at all," John said.

"It was like having an extra knee between two sections of my leg."

John was in the hospital for four months and when the couple returned to Tasmania that December, John's leg cast stayed on for another 10 weeks.

Fast forward to a family holiday in 2010 and they were reunited with Lord Ribeiro, after a chance encounter at the House of Lords.

The former surgeon still recalls that day in 1972.

"It's quite extraordinary ... it's not every day in hospital that you get called up to a case like John's," he said.

"It was an absolute fluke that the woman survived, and the baby survived too."

It took a long time for John to recover from his injuries. ( Supplied: John and Katy Woodroffe )

'This is a photo of a wonderful couple ... '

At the time, John and Katy were the focus of widespread media coverage in London and Tasmania.

Now, 47 years later, John has set out to write a memoir about the incident and the events that followed.

Updates of John's condition were published in English newspapers. ( Supplied: John and Katy Woodroffe )

This process has prompted the couple to revisit the event and the questions that have been left unanswered.

Their friend, Marguerite Scott, shared a post last month on Facebook about the couple's story in the hope that it would help fill those gaps.

Katy and John want to know more about the woman who struck them and her then unborn child.

"We were all in the same hospital at the time but never made contact," Katy said.

"We would just love to fill in some gaps," she said.

The post has caught the eye of history buffs in both the United Kingdom and Australia, and has since been shared over 3,000 times.

"It's amazing how many people have shown interest in it," John said.

Jodie Ernst was keen to help.

"If anyone knows the Tasmanian or English people related to this story, lets help them get in contact with each other," she said.

Faye Houston also got in on the story.

"Sharing it on Marguerite Scott. It would be amazing if anything comes from it. What an extraordinary story!" she said.

Over the years since the accident, the Woodroffes have heard stories of friends running into people overseas who knew about the incident and what happened to the mother and child.

Some have even claimed to have met the now-adult child.

"We had heard about some Tasmanians at the dawn service in Gallipoli years later, and there were some people behind them talking about our accident," John said.

"They engaged in a conversation with the woman who was talking about it, and she said she was the daughter of the woman that jumped that day.

"We would really like to know who those people were."

The incident was covered widely in the news media. ( Supplied: John and Katy Woodroffe )

Katy said: "Finding out that she likely had a daughter has been the most surprising for us".

While the research has been revealing for the couple, one point remains a priority.

"We are very respectful of this woman's family and understand that they may not want to know anything about us or what happened," Katy said.

The future is unwritten

After returning to Australia in late 1972, the Woodroffes worked to get on with their lives.

"We've had 40 years just ignoring it, totally ... we just wanted to get on with it," Katy said.

Both went on to have successful careers as teachers in Launceston, and they are now happily retired and living in Hobart.

So, how did that day in March 1972 change things for Katy and John?

For one, John has a permanent limp and a reduced lung capacity.

Katy and John would love to meet the child of the woman that changed their lives. ( ABC News: Megan MacDonald )

"No marathons for me anytime soon!" he laughed.

Katy added that the experience reminded them how quickly life can change.

"It made us realise that life is so very fragile, and how important it is to make the most of every day," she said.

"Don't take life too seriously — that's been a big part of how we lived our lives since."

Katy and John are heading to Europe this week as Katy starts an artist residency.

They have allowed time to go to England if they do get any leads.

"We do wonder if the people on the other side of this story would like to meet us. We hope so anyway," John said.