The £1.2bn Northern Line extension just reached a major milestone: It has finished tunnelling work from Battersea to Kennington | City PM

The £1.2bn Northern Line extension to Battersea notched up a fresh milestone today, with the completion of tunnelling work.

A huge tunnel boring machine broke through this morning at Kennington, meaning two 3.2km tunnels from Battersea Power Station, via Nine Elms, have now been built.

Since starting in April, two boring machines – dubbed Helen and Amy (tradition dictates that the machines can’t start work until given a name) – have been beavering away to create the north and southbound tunnels extending the Charing Cross branch of the Northern Line.

(Click or tap on the images to see them in full screen)

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Mike Brown, London’s transport commissioner, said:

I’m delighted to welcome the two tunnelling machines to Kennington after their epic journey. Both machines have had to navigate a challenging, congested path under south London which included sewers, power cables, a Victorian-era well, and existing Victoria and Northern line tunnels.

This achievement brings us a significant step closer to the delivery of the first major Tube extension in nearly two decades.

The extension is due to be completed in 2020, and will be the first major extension to a Tube line since the Jubilee Line in the late 1990s.

Each boring machine is capable of tunnelling up to 30m a day with teams of around 50 people operating them.

London mayor, Sadiq Khan, said: “Today’s breakthrough is a momentous moment for a project that is going to bring huge benefits to south London.

“The Northern Line extension is not only going to make travelling to Battersea and Nine Elms easier, it’s also going to bring tens of thousands of new jobs and homes to the area. It’s another great example of why new infrastructure is so vital to London’s success and the wider economy.”

How the Northern line will be extended (Source: TfL)

Timeline of the Northern Line extension

2017 – Main tunnelling takes place

2019 – Station fit out

2020 – Testing and commissioning; extension in operation