Stage one of a flagship tunnel being built below the Thames is complete after engineers successfully sunk a 30 metre shaft in the grounds of Royal Hospital Chelsea .

National Grid Gas Distribution will now shift its focus to Battersea, on the other side of the river, as construction of the 330m long tunnel continues.

The project is part of the National Grid’s £1 billion investment in replacing ageing gas mains across the capital, and is being built to future-proof London’s gas infrastructure for the 21st century.

The Battersea phase of the project is expected to be completed in August, after which tunnelling under the River Thames will begin.

The Royal Hospital Chelsea
The Royal Hospital Chelsea is home to the Chelsea Flower Show

The tunnel is being carved out by a micro tunnel boring machine (TBM), which is remotely controlled by an above ground operation.

The tunnelling phase is expected to be completed sometime in 2018 after which the new intermediate pressure gas pipe will be installed.

The site on north of the river, home to the famous Chelsea Pensioners, has now been cleared to avoid disruption of future events, such as the Chelsea Flower Show , which takes place year from May 23 to May 27.

Andy Hickling, the director of estates, facilities and Quartermaster at the historic hospital, said: “We fully understand the importance of this project but initially we did have concerns that a project of this scale could adversely impact the major events we hold such as the Chelsea Flower Show, (arts fair) Masterpiece and the Global Champions (show jumping) Tour.

“I’m pleased to report that these concerns have not materialised and we could not have wished for a more cooperative and highly professional workforce.”

The hospital is also home to the Chelsea Pensioners

Project manager, Andrew Hejdner, said: “I’d like to thank the Royal Hospital Chelsea and its residents for their patience and understanding over the past few months while we’ve been carrying out work in their grounds.

“We’re working to a very tight schedule and we had to be off the Royal Hospital site by the end of March to make sure events such as the Chelsea Flower Show weren’t affected by our project.”

A plan of the work being carried out

He added: “Our team have got to know many of the residents some of whom served as military engineers or who went onto become engineers after leaving the forces.

“We’ve had some fascinating conversations with them and it turned out that one of the guys had worked on the Channel Tunnel project.”

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