Scottish Transport Minister Keith Brown says today is an historic day as track-laying officially gets underway near Edinburgh.
A state-of-the-art machine has been brought in to lay down the 30 mile track, which will take just over two weeks to complete.
The Borders Railway is expected to establish passenger rail services by September 2015.
"It is genuinely an historic day to see the track being laid for the first time in 40 years bringing the railway back to Midlothian and the Borders. It is a hugely exciting for local people, as this is the biggest domestic railway project in terms of length of rail in the UK for 100 years."
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