For 17 years, a retired train driver and his transport police pal hunted for a missing piece of Manchester's railway history.
Now, their detective work has paid off.
The artifact, which recalls the Victorian age of steam, is finally on its way back to Piccadilly Station.
The Manchester and Birmingham Railway plaque - a high quality replica of the 1839 original - was a erected in the mid-1960s.
It was removed in 1998 when upgrade work began at the station.
It never reappeared when the work ended in 2002.
Railway enthusiast Mel Thorley, 72, then a train driver, noticed it was missing.
Its disappearance unexplained, Mel, from Stockport, began a dogged pursuit - that would last 17 years.
Mel told the Manchester Evening News: "It's not made of brass or copper, so it hadn't been melted. It was so big and heavy, needing a fork lift truck to move it.
"I knew it had to be out there.
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"For 17 years, I studied every railway auction catalogue. I also spoke to the owner of every auction house and supplied them all with a photograph.
"Not a sniff, until, on August 17, it turned up on eBay, for sale in Retford."
The plaque was up for sale with a price tag of £3,700. The sales blurb recommended a forklift to load it onto a truck for collection in Nottinghamshire.
Mel said: " I couldn't believe my eyes. I checked with Dave, my ex-copper friend, who said 'I know that plaque. It's the missing one'.
"I hoped nobody else recognised its significance because I didn't want it to go missing for another 20 years."
Mel's friend, retired British Transport Police officer Dave Smith, 72, contacted the National Railway Museum in York, which confirmed they had the original plaque.
This made clear for Dave and Mel, who both worked at Manchester Piccadilly, that there were in fact two such plaques - the second of which was the missing one they had discovered.
Mel sent emails to alert people in the know, including experts at Railway Magazine.
The magazine had previously run a piece from Lord Faulkner of Worcester, co-chair of the Railway Heritage Designation Advisory Board (RHDAB), requesting readers keep their eyes peeled.
Chris Milner, editor of Railway Magazine, contacted Lord Faulkner, also president of the Railway Heritage Association. He brought in Sir Peter Hendy, chairman of Network Rail, and together they asked BTP for help.
A few weeks later, on September 12, the plaque was retrieved by BTP, citing Network Rail as the item’s rightful owner.
Plans are now in place for the historic sign to be brought home to Manchester Piccadilly station.
Mel said: “I’m chuffed. My mission is now complete.”
The opening of the Manchester & Birmingham Railway in 1839 marked the inter-city railway’s first steps south towards London. This followed the opening of the world’s first inter-city railway in 1830 between Liverpool and Manchester railway.
Lord Faulkner said: “Recovery of this precious artifact is terrific news and casts tremendous credit on the BTP, Mel Thorley and Network Rail chairman Sir Peter Hendy. I will now recommend to the RHDAB that the plaque be designated and protected by law.”
Detective Sergeant Gemma Jones of BTP, said: “This historic plaque went missing 20 years ago, so retrieving evidence and knowledge of the incident was no easy task.
"The team, alongside Network Rail, secured the plaque and we now look forward to seeing it displayed at Manchester Piccadilly.”
