In the 1930s, the London Underground looked at extending the Bakerloo line southwards, and while most plans were modest, one looked at taking it all the way out to Dartford.

This was thanks to a suggestion from Southern Railway to let London Underground take over one of its lines so that it could redeploy its existing trains to other lines and reduce congestion.

Thus in 1936/7 a report was commissioned to look at the viability of an extension of the Bakerloo line to Camberwell Green and Peckham Rye and then over the existing mainline tracks to Barnhurst and Dartford. The idea was to extend the Bakerloo line in a tunnel from Elephant and Castle, via Camberwell Green and then rise to the surface and join the mainline railway at around Vestry Road near Peckham Rye.

A spur down to the now-closed High-Level station at Crystal Palace was also considered.

Various works would be needed to widen the railway so that it could be shared by both Southern and the London Undeground, and a major piece of work would be needed at Lewisham to create space for the tube trains.

The London Underground would then take over the entire Southern service via Bexleyheath to Barenhurt, then with fewer trains on to Dartford as well.

One of the quirks of the report is that it refers to the extension as being to Barnehurst and Dartford. This was to deal with the problem that the London Passenger Transport Board was authorised to run services up to 12 miles from Charing Cross — aka, to Barnehurst, and they either needed a waiver to extend to Dartford, or worst case, might need to run an independent shuttle between Dartford and Barnehurst.

The proposal was costed at around £4 million, but as it would only bring in around £60,000 in extra revenues for the London Underground, that put the return at just 1.5%, which was low for the time. It’s notable that they would have made a profit on the extension, but it was too close to running a loss, which is why the scheme never progressed any further.

Today of course, to build a railway extension and make a profit on it alone would be a minor miracle, and transport upgrades are usually funded by looking at the wider society benefits, and if the economic gain for everyone is good, then transport upgrades can be supported by government as well as the direct fares income.

But back in the 1930s, trains had to pay for themselves, and this made the project look unlikely — but they looked anyway, just in case.

The report noted that while the provision of an Underground service on the Barnehurst line would stimulate traffic, they were doubtful if the “lower middle class and working class” populations of the area would use the line.

Part of this was due to the different pricing used by the London Underground of around 1d per mile and Southern Railway of 1.5d per mile. If London Underground raised its average fares, it would get fewer customers, but if Southern were forced to lower its fares, it might not see enough additional passengers to cover its loses.

This was seen as a very serious issue, as it would be very difficult for the London Underground to charge different rates depending on which part of the Bakerloo line you were using, and would be seen in a poor light by the travelling public.

Today of course, with fares set regionally across transport services, that’s not such a big issue, but back in the 1930s it caused a lot of concern.

The Bakerloo line station at Camberwell Green would help reduce congestion on the Northern line at Oval and Kennington, but it might have reduced ticket sales at Elephant and Castle, and at the time, stations had to pay their way through ticket sales. Fewer sales at Elephant and Castle would be seen as a very bad thing if you were the local manager.

And of course, when you extend railways and run more trains, you need more space to store the trains. They eyed up a plot of land owned by Southern Railway at Kidbrook, and less desired, at Slades Green. On the upside, from their perspective, this would let them close the existing Bakerloo line depot at London Road in Lambeth, and sell off the land for development.

However, with the limited fares revenue being expected, the £4 million cost, even supported by the New Works Programme was still seen as to high a risk, and that with the available funds, it was more important to deal with overcrowding issues elsewhere, particularly on the Northern line to Morden.

Although the project was put on hold, they still sent their report to Frank Pick, Vice-Chairman of London Transport in July 1937.

They summarised that the scheme was not very promising, from a financial point of view. This was at a time when the costs of public transport upgrades had to be funded by the passengers alone, and couldn’t as today, rely on government funding due to the wider society benefits an upgrade offers.

That major difference is why the Bakerloo line extension was not viable in 1937, but would be in 2020.

This article is based largely on documents at TfL’s corporate archives: LT000254/1545