A visit to Scotland by the famous steam locomotive the Flying Scotsman will not go ahead as planned after a last-minute decision by Network Rail.
The track operator said it had not been able to carry out assessment work on some lines in time for the tour, which organisers say has been in the planning for more than a year.
The Flying Scotsman will operate between York and Edinburgh Waverley on Saturday as scheduled, but a vintage diesel engine is expected to take over for Sunday's trip, which was to see it run on the new Borders Railway to Tweedbank and across the Forth Bridge.
The decision will disappoint hundreds of rail enthusiasts expected to turn out to see the recently refurbished steam engine.
Excursion operators Steam Dreams said: "Network Rail has known about these trips for months and they have left this gauging until the last minute.
"It means there is absolutely no time to plan anything else for the locomotive so we can give passengers in Scotland a trip behind this icon."
Built in Doncaster, South Yorkshire, in 1923, the Flying Scotsman pulled the first train to break the 100mph barrier in 1934.
The National Railway Museum in York bought the locomotive for £2.3 million in 2004 before work got under way on its decade-long restoration two years later.
Network Rail was forced to pay out almost £60,000 in compensation when dozens of train services were delayed by people encroaching on the track during the refurbished train's inaugural run from London to York on February 2 this year.
A spokesman for the operator said: "The routes the Scotsman had planned to cover this weekend are new ones for the locomotive and have to be individually assessed by our engineers in advance.
"Unfortunately we have been unable to carry out the work in time and cannot allow the engine to run when we are unsure if the unique design of the Flying Scotsman is compatible with the current railway infrastructure across the Fife and Borders routes.
"We understand the disappointment this will cause all those who had been looking forward to the iconic engine returning to these parts of Scotland and a full investigation will be undertaken into why these issues were not identified sooner."
A spokeswoman for the National Railway Museum said: "We are sorry to hear that our locomotive Flying Scotsman will be unable to haul the May 15 Steam Dreams The Borders Scotsman and Fife Evening Circular tours, due to an administrative issue.
"We can confirm there is nothing mechanically wrong with the engine which makes its triumphant return to Scotland post-restoration on Saturday May 14 with the York-Edinburgh leg of the Cathedral's Express service.
"We share the disappointment of the people of Scotland who were hoping to catch a glimpse of Flying Scotsman on its travels through Fife and the Borders."
The Flying Scotsman will be displayed at the Bo'ness and Kinneil Railway on Monday as planned, with an extra day on Sunday.