Network Rail, over the past 10 weeks, has been making repairs to the Blackheath tunnel.

The historic tunnel, which runs between Charlton and Blackheath stations was in need of strengthening and waterproofing to allow trains to remain reliableable.

Services were diverted during the repair work, and today, have now returned to normal timetabled services.

The 175-year-old structure has undergone an extensive strengthening and waterproofing process.

Engineers have injected grout into pockets of sand and gravel which surround the tunnel to help keep the ground strong.

Further grout was applied to the back of the tunnel lining to help with waterproofing in the worst-affected areas.

The innovative technique has been successful on the Blackheath tunnel and will be used across other parts of the railway.

“Over the last 10-weeks we’ve completed a groundbreaking programme in the tunnel that will improve reliability by strengthening and waterproofing the structure to better protect the railway.

“Savings from this approach are estimated to be around £10 million and this can be reinvested across the network to deliver more improvements that will keep passengers moving.”

“Last summer our engineers cleaned soot from the tunnel lining, carried out detailed surveys and replaced thousands of bricks to stop water getting in. This year we’ve installed a new tunnel lining, rebuilt drainage systems and completed essential track work, including the removal of the waterlogged sections known as ‘wet beds’.

“I want to thank our customers for bearing with us while the tunnel was closed for this work to deliver better journeys.” 

David Davidson, chief operating officer for the South Eastern Railway