London is about to get a new tunnel, albeit a short one, as the National Gallery plans to link two buildings via an underground tunnel so the public can walk between them.

It’s part of the NG200 redevelopment of the National Gallery’s Sainsbury Wing, which identified a number of problems with the current layout. At the moment, people generally go in via the ground floor, up the stairs/lift and then connect to the older building via an elevated walkway, and leave through the older building.

But the single route between the two buildings makes it harder to come back again, especially as the cloakroom is by the entrance, and people need to double back along that one elevated walkway to collect their bags and coats.

So, part of the rebuilding work will see a brand new tunnel added in the basement that will make visitor flow between the two buildings much easier.

The new link will bring visitors directly to and from the older Wilkins Building – specifically to the location of the newly expanded Research Centre rooms and Members’ House – but equally to a new public stair and lift that will connect to the Main Gallery level. This will provide for more circulation options that do not require retracing one’s steps.

Once the tunnel is opened, it’ll be large enough that it’s unlikely that many people will even realise they are walking through a tunnel linking the two buildings.

Unsurprisingly, as part of the preparations for the new tunnel to be dug under the pavement above, they’ve had to check if there’s anything else in the area. That’s more significant than you might expect.

Before the Sainsbury Wing was built, the site was used as a construction site for the Jubilee line, with two long access tunnels dug under Trafalgar Square to Charing Cross. That tunnel is still there, and in fact, you can visit it as part of the LT Museum’s Hidden London tours, but the National Gallery needed to make sure it wouldn’t interfere with their tunnel.

In fact they don’t — as the access shafts that were dug down were later removed down to about 25 metres below ground, and the base capped with concrete.

The National Gallery’s new tunnel will go down 8 metres, so won’t hit the old Jubilee line construction tunnels.

But they had to check. Just in case.

A spokesperson for the National Gallery confirmed that work has now started on excavating the new tunnel, which will also include the side wings on either side of the tunnel for the new cloakroom and toilets.

The link will open when Phase 2 of the NG200 project is completed, and London gains another tunnel to add to its subterranean maze.