When divorcee Ian Lowther answered the door at his Baildon home on Saturday, April 8, 2000, he was met by a team of Bradford detectives.

They had come to arrest him for the murder of Shipley housewife Mary Gregson - 22 years and 211 days after the discovery of her body in the River Aire.

Lowther, a father-of-one, was on the original list of 9,000 suspects drawn up by murder squad detectives in the late 1970s.

He was among 830 builders working on construction of the Inland Revenue base in Shipley during 1977.

Police first spoke to him two days after the murder and interviewed him again a few weeks later during house-to-house inquiries.

When the Gregson murder investigation was re-opened last summer detectives began to work their way through the list of 9,000 in the hope of finding a DNA match.

Many of the original suspects had moved away from the area and their search for the killer stretched across Britain.

Ironically, the man detectives were desperate to find lived only a few hundred yards away from the spot where Mary's body was discovered.

Lowther was the 535th suspect visited for a swab test on Feb 27, 2000. Two months later the results came through - it was a DNA match.

Within hours a team of officers had been despatched to Lowther's home in Derwent Avenue - a quiet street in Baildon on the banks of the River Aire.

Until then the 47-year-old had lived with his grim secret for three decades. He was aware the case had been re-opened and duly volunteered to take part in the swab test.

When he was told of his arrest Lowther showed no emotion.

So much so that he asked detectives to wait for him while he placed his slippers behind the front door in anticipation of his return home.

He was never released from custody and, before his final Court appearance, Lowther instructed solicitors to put his house up for sale.

The passage of time has seen a distinct change in Lowther's appearance - from the gaunt young man who sexually assaulted and strangled Mary Gregson to the stocky grandfather with grey receding hair who stood in the dock at Sheffield Crown Court.

Police describe him as a loner and otherwise model citizen. Methodical and meticulous, he was well-liked by work colleagues and known as "Uncle Ian" to his friends' children.

After the re-opening of the case detectives enlisted the help of a 'Cracker' style psychologist to track down the killer.

But the character profile drawn up to help solve the mystery which had spanned three decades turned out to be wide of the mark.

It suggested the murderer may have come from a poor background, may have been abused as a child and had committed other crimes.

In fact, the man responsible for the brutal killing has been described as the perfect neighbour and family man.

Lowther, as far as police know, has not committed any other serious crimes apart from the murder. His only previous brush with the law logged on police records was for a fixed-penalty speeding ticket.

His daughter, former wife and four grandchildren all still live in the Baildon area. Lowther's love of the countryside may explain why he resisted the temptation to move away after the murder.

Since his divorce in 1999 - when he set up home on his own in Derwent Avenue, Baildon - neighbours say he lived the life of a virtual recluse.

He kept himself fit by working out at a nearby gym but, in a tight-knit community, he never used local shops or visited nearby pubs.

One neighbour in Derwent Avenue recalls: "He was a quiet man who kept himself to himself - a bit of a recluse. None of the neighbours really knew him and never imagined he would be capable of this."

Another neighbour added: "The Gregson murder posters were put up all around this area last year. He must have seen one every day."

A neighbour from Central Avenue, Baildon - where Lowther lived with his wife and daughter at the time of the murder - said: "There's nothing bad to say about him other than he's a lovely man.

"I've known him for years. The kids all liked him and we couldn't have wished for a better neighbour. It came as something of a shock when we found out he'd been arrested."

Ian Richard Lowther spent most of his early life in North Yorkshire.

Born on October 29, 1952, in Harrogate, he was from a respectable middle class family and the youngest of two sons.

His father worked as a chauffeur for a Yorkshire mill owner and his mother was a housewife.

Lowther was educated in Harrogate and eventually left school at 16 with no qualifications.

He started a three-year apprenticeship at Harrogate Technical College - a move which would lead to his first connection with Shipley.

Staff at the technical college booked him on a day release course at Shipley College - where he was to meet his future wife Carol.

The couple married in Harrogate on May 11, 1973, and set up their first home at a council flat in Denby House, Denby Drive, Baildon.

Later that year their only child Carmen, now 27 and still living in the Baildon area, was born.

The family stayed at Denby Drive for three-and-a-half years before moving to a bigger house two streets away - in Central Avenue.

At about the same time, in November 1976, Lowther started work as a labourer for John Laing & Co at the Inland Revenue building site in Shipley.

While he was working on the site he murdered Mary Gregson on the towpath of the Leeds Liverpool Canal and then dumped her body in the River Aire.

Despite a massive amount of publicity and appeals for information about the killing Lowther slipped through the net and left Laing's a few weeks after the murder.

But he resisted the temptation to move away from the scene of his crime and stayed in the building trade, working as a labourer with several firms in Shipley and Baildon.

By the time he eventually changed careers in 1986 - taking on a job at British Mohair Spinners in Baildon - Mary's husband Bill, haunted by who killed his wife and why, had died.

The murder inquiry lay on police files and was not closed, but updates and appeals for information had not featured in the media for five years.

At the start of the 1990s Lowther was made redundant and changed careers again, securing a job at Tri-Print Ltd in Bradford city centre.

He worked in the warehouse and as a elivery driver and was regarded as an excellent and conscientious employee.

In 1998 Lowther and his wife separated. By the time they divorced in 1999 detectives had decided to re-open the Mary Gregson murder inquiry after a breakthrough in DNA technology. Lowther moved to Derwent Avenue, buying the house from his daughter, where he lived until his arrest.