Metropolitan Line tunnels between Finchley Road and Baker St

[downdc]

Hello all

I have been prompted to ask about this on here by a recent thread on the railuk forums, regarding something I am curious about, namely, the tunnels mentioned above.

Specifically, I am interested to learn about the construction methods used for these tunnels, and in particular about their interaction when built with the extant mainline Primrose Hill tunnels, between South Hampstead and Euston stations.  There are of course many famous images of the cut-and-cover construction of the original Metropolitan Railway, and much reference to the disruption this caused.  Other than online, I have not read at all about the history of what is now LU; whilst I am sure that the original Metropolitan Railway construction will have been extensively covered, the thread I refer to mentions that there is something of a paucity of information regarding the extension.  I remember hearing that certain elements of the tunnel construction here are unique, I think in threads about the renewal works which have been required recently, and in searching for the topic I found some comments which suggest there is uncertainty about construction methods etc.  I am aware that there is a section with separate tunnels for each running line; on the comments I found when searching, questions arose as to whether the term ‘single bore’ was in this case accurate or in fact simply referring to the single track nature of the tunnels.  Whilst I have no idea, the appearance of the walls and other elements of the construction where visible at the disused stations and other open sections looks so similar to that of the original MR route that I have to feel the likelihood is that the tunnels are cut and cover.

As mentioned though, I am most interested to know about how crossing the extant tunnels at that time was tackled.  I know the clearances aren’t comparable to what was involved with threading Crossrail through the centre of London, but given the time period concerned, impressive nonetheless! I’d be fascinated to learn about it, even more so to see any images, akin to the various well-known ones from the construction and early days of the MR.


Does anybody have their own information or knowledge to share, or is anybody aware of any reference/resource of information on the topic?

As always, thanks in advance!

[zbang]

You may find something in Reconstruction London's Underground (Follenfant), I don't have the time to look at the moment.

[downdc]

Thanks!

[jimbo]

Didn't the branch north from Baker Street start out as a single-track extension?

[downdc]

Yes, as per history which is available online, this still would have involved crossing the mainline tunnel however. In actual fact, it only raises more questions regarding the formation, it surely can’t have all been entirely rebuilt for double track?? After all, AFAIK the only single track tunnel section now is immediately before/after Finchley Road, where the Met is either side of the Jubilee.

[programmes1]

May 31, 2023 9:05:26 GMT downdc said:

Yes, as per history which is available online, this still would have involved crossing the mainline tunnel however. In actual fact, it only raises more questions regarding the formation, it surely can’t have all been entirely rebuilt for double track?? After all, AFAIK the only single track tunnel section now is immediately before/after Finchley Road, where the Met is either side of the Jubilee.

Just a thought perhaps the LT Museum at Acton could help as they may have all the drawings. There is also the Metropolitan Archives as well as the National Archives.

[downdc]

Thanks for those suggestions, I’ve not previously thought about what one could find in such archives!

[xplaistow]

From what I remember, most of this section continues to be single bore tunnels with the only double track sections being around the closed stations of Lord's*, Marlborough Road & Swiss Cottage.

(*This stretch includes the open-air crossing of the Regent's Canal.)

[Chris L]

May 31, 2023 14:39:18 GMT xplaistow said:

From what I remember, most of this section continues to be single bore tunnels with the only double track sections being around the closed stations of Lord's*, Marlborough Road & Swiss Cottage.

(*This stretch includes the open-air crossing of the Regent's Canal.)

From working on the former Swiss Cottage Met platforms to survey air conditioning equipment for the Jubilee line station I remember that they were close to the surface.

There is access through doors in one of the subways leading to the Jubilee line ticket hall.

[downdc]

May 31, 2023 14:39:18 GMT xplaistow said:

From what I remember, most of this section continues to be single bore tunnels with the only double track sections being around the closed stations of Lord's*, Marlborough Road & Swiss Cottage.

(*This stretch includes the open-air crossing of the Regent's Canal.)

You may well be correct, I haven’t paid attention to check carefully even though I did travel Northbound through this section a few days ago.

Yesterday I had a walk around all of the spots you mention, including sitting on top of the ventilation grille above Swiss Cottage so I could see down onto the track and trains below.  Unfortunately, it turns out I am somewhat shorter than the Google streetview camera (no duh) and therefore my views at the other two spots were very limited! Although, there is a little bit of wall to perch on by Marlborough Road, and the crossing of the canal you mentioned is easily viewable from the towpath and steps down to it, as are the adjacent Chiltern Line bridges. The limited view I could get down at the open air spots was the basis for my earlier comment on the visual similarities with the original MR open sections, particularly between Kings Cross and Farringdon.

[downdc]

May 31, 2023 18:07:05 GMT Chris L said:

May 31, 2023 14:39:18 GMT xplaistow said:

From working on the former Swiss Cottage Met platforms to survey air conditioning equipment for the Jubilee line station I remember that they were close to the surface.

There is access through doors in one of the subways leading to the Jubilee line ticket hall.

As per the previous post I was sat at street level watching trains pass at a very shallow distance below

[Hutch]

From Badsey-Ellis (2016) "Building London's Underground", p. 43:

"...work started in 1865. It was constructed beneath the roads in a single-track tunnel, this being both for economy and also to save having to obstruct the streets completely during construction work." In this, he quotes "The Engineer", 27 January 1865*.

From the above, all though not entirely clear, it appears the tunnel was dug underground in the main and was not cut and cover as I would have imagined considering its shallow depth.

It continues: "The tunnels were constructed of brick with arched crowns".

Further on page 47: "Perhaps surprisingly, the line between Swiss Cottage and Baker Street remained single track between the stations until July 1882, when new tunnels to the east of the original tunnels were opened to carry a new 'up' line (i.e., trains towards London)."

The above, while giving a date, is silent on exactly how they were constructed but I suspect it was the same as the 1865 tunnels.

Later edit:

*You can read the original reference here. Having read it carefully, I conclude it was constructed as cut and cover ("covered way" is the term used), but as a single track only so as to minimise the interference to the surface roads and for economy.

[downdc]

Thanks Hutch, it certainly makes much more sense, and ties in with what xplaistow says about most of the covered sections being single track. I still wonder about the open sections, my understanding of civil engineering and the history thereof is almost zero, so it seems as if it would have been difficult to rebuild open sections for widening, but I could well be totally off on that!

The specific part which I find by far the most interesting, which is the intersection of the Met and Primrose Hill tunnels, remains elusive! Nonetheless, I greatly appreciate the response and input so far

[Hutch]

Jun 1, 2023 12:51:22 GMT downdc said:

The specific part which I find by far the most interesting, which is the intersection of the Met and Primrose Hill tunnels, remains elusive! Nonetheless, I greatly appreciate the response and input so far

It is useful to look at this map which has spot heights on it. The crown of Primrose Hill Tunnel can be estimated by the 131' mark of the Loudoun Road bridge. There is a spot height on the road over the Met tunnels where they cross the mainline tunnels at 175'. This suggests there is a clearance of 44' to fit the Met Line tunnels which is more than adequate.

[downdc]

Thanks again; adequate without question, it still strikes me that vertically separated tunnels crossing below ground was somewhat novel at this point in time, and I am often fascinated by these arrangements, across the range of their complexity

[downdc]

Jun 1, 2023 15:25:09 GMT Hutch said:

Jun 1, 2023 12:51:22 GMT downdc said:

Although, having looked at the map, it doesn’t seem to me that the Metropolitan tunnels are actually shown, the tracks as shown above ground seem to disappear east of Finchley Road station, as compared to the depictions of the (modern day) Chiltern, WCML and DC tracks when they go into tunnel. I could, of course, be interpreting it incorrectly 

Edit to say I’ve obviously made a dog’s dinner of trying to trim down the quote!

And, a further edit as having re-read and re-checked I note you’re referring to the height of the road where the tunnel crossing takes place, as opposed to the Met tunnels being depicted; apologies!

[Chris L]

Jun 1, 2023 16:02:20 GMT downdc said:

Thanks again; adequate without question, it still strikes me that vertically separated tunnels crossing below ground was somewhat novel at this point in time, and I am often fascinated by these arrangements, across the range of their complexity

The Central line tunnels at St Paul's and Chancery Lane are on top of each other and cross over as necessary.

When built the railway had to own to property above the tunnels. This arrangement reduced the ground level cost.

[downdc]

I love the Central Line side-swap west of White City, which is visible from a footbridge. I love the Widened Lines crossing under the Met/Circle west of Farringdon, I love the swip-swap and reuse of the tunnels south of Finsbury Park, the junctions south of Camden Town, standing on the platforms at Aldgate and being able to see the various underground junctions just as they show up on the regular map, and on the mainline I love the interweaving at Camden Junction and Primrose Hill near Euston, or the huge multi-level criss-cross just outside Kings Cross and St Pancras but… I really do digress, particularly on the last two, even if they do both include contemporary TfL services! Forgive me