Just under 100 years ago, an extension of the Northern Line running under the Thames opened to the public, but 26 years later it would be hit by a German bomb and flooded. It is still sealed off to this day.

The short length of tunnel ran from Charing Cross down to Embankment and back up again via a loop under the Thames. Although I said most of the tunnel is still sealed off following that attack, a small part of it is still accessible, and in fact, used as a convenient storage location by London Underground.

It also contains stalactites!

A couple of years ago, I wrote in depth about that tunnel and the German air raid that flooded it. Subsequent to that I was sent some photos by someone who had permission to go inside the accessible bit of the tunnel, so this is a timely follow up to that earlier article — as today is the 73rd anniversary of that German bombing raid.

All the photos are copyrighted to the photographer, and that person kindly gave me permission to publish them here.

To provide a bit of context, here is a map of the Northern Line loop tunnel that opened in 1914, but was abandoned in 1926 when the Northern Line was extended down to Kennington, where it ended, appropriately enough, in another loop.

The orange tunnels are today’s Northern Line, and the green is the bit of the loop that is still accessible to tube staff.


Needless to say, there is no public access, and having been sent a photo of the entrance from the outside, it is not in a location you could get to particularly easily. I am not putting that photo on here – sorry!

But here is the inside of the tunnel.

xEmbankment Loop 2a

A bit further down the tunnel — notice the curious break in the tunnel lining halfway down the photo and how it widens slightly for a few tunnel rings width. No idea why.

xEmbankment Loop 4

A bricked up side tunnel – not sure of its origins, but there is a small side tunnel on the map which could be what this was. Possibly left over from the earlier construction as it appears to be too small for public use. It might have been later reused for ventilation?

xEmbankment Loop 5a copy

Towards the concrete bulkhead that marks the end of the tunnel

Embankment Loop 7 copy

The end of the tunnel — beyond that concrete wall is/was an access shaft for ventilation, and just past that is the second bulkhead wall that fortunately had been installed and stopped the Thames flooding into the rest of the Northern Line.

xEmbankment Loop 9

Some day, someone will have to open that bulkhead door and go in to inspect the state of the tunnel. What a wonderful experience to be in a tunnel that no one has been in for over 70 years, and to touch the concrete filled sandbags that are presumably still there – holding back the Thames ever since they were hurriedly put in place in September 1940.

Now go and read about the bombing of the Embankment Loop.


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  1. Jim Fearnley says:

    One or two are reminiscent of nautilus shells – beautiful.

  2. Andre says:

    That’s sooo cool!! I wish I could visit it!! Every time I go to Gordon’s now I will think that there is a tunnel underneath it.. and look for the entrance 🙂

  3. Chris Sullivan says:

    I have always known the existence of the disused loop and of it’s bombing during the war but did not know, although I have always suspected, that access was still possible (and I used to work on the UndergrounD). I suspect that entry is via a door in the left hand side of the southbound tunnel about 50 feet after the end of the Charing Cross, (Strand) platform where there is a noticeable drop where the extension and the loop diverged

  4. Londona729 says:

    I would love to walk through this tunnel!

  5. Musicmaestro says:

    The bricked up opening is most likely the ‘disused heading’ marked on the plans.

  6. Charlie Connor says:

    The side tunnel is curious. It has to be the one marked as ‘disused header’ on the plan, which is also referred to in the bombing report as being reinforces with concrete and brick, presumably the brick facing in the photo being the wartime reinforcement. As to it’s original use, that is mysterious. It appears to lead either from the extreme north end of what is now the northbound platform, or maybe even from inside the n/b tunnel mouth. It would have been an expensive luxury if it did not have a specific use. I wonder whether emergency access was required to be provided in the event of an issue in the under-river section of the tunnel, either to allow staff to access the eastern side of the loop without having to walk the full length, or emergency de-training of passengers. When you see the way it is connected to the running tunnel it seems to be very much part of the original design, and not a later addition. I wonder whether there is anything in the PRO which may shed some light on this.

  7. Ralph Caton says:

    That short segment where the tunnel expands from the C&SL diameter (10′ 6″?) – could that have been a ore 1926 experiment to determine the feasibility of expanding the diameter of the original tube?

    • Philip Roy says:

      Tunnel segments often have the date or other identifying marks cast into them. Should anybody manage to arrange access (a long shot I know!) it might be possible to gain some further information.

  8. Philip Roy says:

    Very interesting, I never knew that the loop had been plugged and drained. I thought that it had just been abandoned.

    The plans are really interesting, are these publicly available? If so where?

    Thanks for putting this article together, your work is appreciated.

  9. Philip Roy says:

    Tunnel segments often have the date or other identifying marks cast into them. Should anybody manage to arrange access (a long shot I know!) it might be possible to gain some further information.

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