The £2.4 million investment will protect the red sandstone, five-arch Listed structure against future erosion by undertaking scour protection and masonry repairs.

Spanning the River Tweed on the Borders Railway line between Tweedbank and Galashiels, work started on the bridge in late April and is expected to complete by October.

Scour protection involves the removal of the existing riverbed around the impacted base of the bridge pier and then installing a scour ‘mattress’ filled with concrete. This helps to shield the base from the damage that can be caused by fast flowing water.

The first phase of work included the installation of 600 square meters of scour mattress and 400 tonnes of permanent rock shield, as well as 150 cubic metres of poured concrete.

To allow the team to deliver the work, a portable dam system was set up under the bridge to help reduce the river flow and create a safe working area.

Ahead of setting up the dam, the project team worked with the River Tweed Commission to relocate fish to another part of the river before water was then drained to form the dry working area - this process will be repeated at each subsequent pier as work progresses.

Christina Thomson, Network Rail’s project manager for the work said: “The team has delivered the first of three phases of work to Redbridge Viaduct; essential maintenance that protects the piers of the viaduct from scour erosion and in turn, helps maintain the railway infrastructure.

“We’ve worked collaboratively with Scottish Borders Council throughout and with the River Tweed Commission and our environmental and marine engineering specialists to ensure our activity has minimal impact to the river’s existing habitat - and will continue to do so throughout the rest of the project.

“The viaduct is an historic Victorian structure that continues to play an important role in carrying passenger trains on the Borders Railway route. When work is complete in October, we won’t need to undertake repairs on this scale for many years to come.”