Britain's Queen Elizabeth will mark becoming the longest reigning monarch by opening a railway line.

Britain's Queen Elizabeth

Britain's Queen Elizabeth

The 89-year-old monarch will surpass her great-great-grandmother Queen Victoria's record on September 9 and will mark the occasion by travelling by steam train from Edinburgh to Tweedbank near Galashiels to open the Borders Railway - the UK's biggest new domestic railway line for more than a century.

Keith Brown, Cabinet Secretary for Infrastructure in the Scottish Government, said: "It is a great honour for us that Her Majesty has chosen to mark this milestone by leading the celebrations for the opening of the Borders Railway.

"The people of the Borders and Midlothian have waited almost half a century to see the return of their railway and it is fitting that these two such historic events coincide.

"This will be a double celebration and we are also ensuring that the people who have campaigned, worked hard and shown such patience throughout this process are able to play a full part in the celebrations, with a separate day dedicated just to them."

Elizabeth - who became Queen on February 6 1952, aged 25 - will be accompanied on the journey by the Scottish First Minister Nicola Sturgeon, with the event acting as a visible reminder of her love of Scotland, a year after the nation held an independence referendum.

The Queen and her husband Prince Philip will be part of opening celebrations at Edinburgh's Waverley Station before embarking on their journey, with the details being announced by Buckingham Palace and the Scottish Government as they finalise preparations for the £300 million line's opening.