Tanners Hill Flydown – Part 1

Our original plan was to write a piece on St Johns station. This would conclude with a short section on the work carried out over the Christmas holidays on the Tanners Hill Flydown. Like many plans produced by the London Reconnections Planning Committee this plan fell apart when events overtook us. Over the past few months Unravelled, LR’s “photographer-in-chief,” has been documenting the recent major railway engineering changes happening to the area just to the south of St Johns station, and this deserves an article on its own. On top of that Tom Burnham has generously provided some wonderful photos of previous work completed in the 1970s, which are helpful as background information. It therefore seems fitting to have an article just on the Tanners Hill Flydown. Part 1 will concentrate on the original work in the 1970s and feature Tom Burnham’s photos and part 2 will use some of Unravelled’s collection to illustrate the recent doubling of the track.

The Tanners Hill Tunnels

Tanner’s Hill is a location between New Cross and St Johns stations in South-East London. Beyond St Johns is Lewisham station. Until the 1970s Tanner’s Hill was synonymous in railway circles with three very short parallel tunnels between New Cross and St Johns stations. They are a mere 87 yards long and consist of a double track central bore flanked by two single track bores. Nowadays it is difficult to see the why the tunnels are there, because all there is above them is a small plot of land that is fenced off for nature conservation. The top of the crown of the main bore is probably only five or six feet below the surface at this point. This article is not about the tunnels though, but a relatively modern rising embankment which was was given the name of Tanner Hill Flydown – this is, in fact, a few hundred metres away from the hill in question.

The 1976 London Bridge Resignalling Scheme

In 1976 the Southern Region of British Railways brought into fruition a major plan to re-organise the lines between Lewisham and London Bridge, so that trains would already be sorted by destination/originating London terminal. At the same time a large area would be resignalled and London Bridge Panel signal box would come into existence.

The plan was well thought out, but it was clear there were one or two complications. One was that any train from platform 3 at Lewisham (from Blackheath) to Charing Cross was going to have to cross ‘on the flat’ to arrive at platform 6 at London Bridge. As this would happen every ten minutes in the high peak, it was going to be a considerable inconvenience and make the desired timetable unworkable. The solution was to take advantage of an existing flyover that crossed the main lines at St Johns and via a steeply banked descent join the southernmost line (up Charing Cross) without crossing any of the other tracks on the main line. The line would be bidirectional to enable the reverse process to happen in the down direction.

Confusingly “up” trains (to London) will go downhill on the flydown and down trains will climb uphill. In the down direction, the train movements would not be quite as optimal as the up direction because the up Charing Cross line would have to be crossed on the flat. It did, however, at least give the signalman an alternative path if for any reason a down Charing Cross train and was not already switched over to northernmost down line, which was the only route available to call at Lewisham station.

The steeply descending route described in the previous paragraph was officially designated “Tanners Hill Flydown”. It was probably given that name to avoid confusion, because there were so many other junctions and bridges in the area. In practice it has been much more of a “flydown” than a “flyup” since the signalmen (or the train planners) have subsequently shown a strong preference to use it in the downhill direction.

The picture above, taken in 1971, shows the site of the abandoned sidings at St Johns which would be built up to create the flydown. The little used island platform visible in the picture would be demolished, the footbridge would be replaced with a less substantial one that would provide the necessary clearance and the leftmost brick arch just visible behind it would need to be rebuilt for the same reason.

The building of the original flydown was a substantial piece of engineering in its own right. Fortunately there was railway land available to build the substantial embankment necessary, but to try and minimise the gradient it was necessary to rebuild a then unused arch. This took a road called St John’s Vale across the railway, and at this point the new flydown would still be a few feet higher than the mainline track. It was also felt necessary to build a substantial retaining wall. This was probably so that the track could join the main line as far west as possible, to minimise the gradient and maximise the turnout speed. Even so the maximum gradient is 1 in 45. Although this is easily managed by electric trains, it must be quite a challenge if a Lewisham-bound train is brought to a halt by a signal at the top of the flydown.

As can be imagined, the construction of this flydown in the early 1970’s caused considerable disruption to local residents. In those days a fairly cavalier approach was taken to construction when it came to inconveniencing local residents. The Code of Construction Practice was completely unheard of, as was agreed hours of working to limit inconvenience from noise. This cavalier approach at the time would cause problems later.

The picture below, taken in 1974, shows the substantial works necessary to provide a reasonable fast speed turnout to join the main lines. The entrance portals to Lucas Street (Tanners Hill) tunnels are in the distance. Note the crossover tracks that were present then. To a large extent the whole purpose of the flydown was to make elimination of this flat crossover possible.

The 1990s and Longer Platforms

Some stations and their surrounding areas seem to survive almost unaltered over periods exceeding a century. Others seem to fundamentally change every few years (or at least every decade or two). St Johns definitively falls in the latter category. In the late 1980s/early 1990s the South-East Division of Southern Region embarked on a major plan to make all its inner suburban stations able to accommodate 12-car trains. St Johns station proved to be a tricky problem. Extension at the country (Lewisham) end was out of the question due to a critical junction. The prefered solution of the railway management would likely have been to close the station. That, however, was not going to happen and thus the only alternative available in the days before Selective Door Operation was to demolish the bridge at the London end of the station and replace it with one that spanned all the main lines. This would then make it possible to extend the island platform under the bridge.

The image below shows the heavily graffitied metal single span built in 1992 to replace the former brick arches. This was taken in Easter 2012 from the extended London end of the platform which was extended to allow 12 car trains to call. Ironically no 12 car trains have ever called at St Johns and the metal span would have to be modified and and a new abutment built to enable the flydown to be doubled.

The metal bridge show above spanned the four main lines. The opening for the flydown, which replaced one of the original arches, was left alone. The result was rather ugly but functional and at the time appeared to be the cost-effective solution. In those days the Treasury had a strict rule preventing railways future-proofing construction without being about to produce a convincing business case for any future enhancement. The only relevant project that could conceivably be on the horizon was Thameslink 2000. This was in the early stages of planning, there was no certainty it would happen at all, let alone go through St Johns.

Thameslink 2000

By the early years of the 21st century Thameslink 2000 was being taken seriously and definite plans were taking shape. At the time a firm favourite for a Thameslink route was one of the lines to Dartford. By the time plans were laid before a public enquiry it had been decided that it would be necessary to double the Tanners Hill Flydown. It was never quite make clear why this would be necessary if Thameslink merely took over one of the Dartford via Lewisham routes. Was it to aid reliability or to enable an enhanced service to be offered?

It was here that the previous disruption came back to haunt the new project. Communities have long memories, and at the Thameslink Public Enquiry the residents of St John’s protested vehemently against the proposals. They described in detail the noise and disruption that they had been subjected to when the flydown was originally built and thought it unreasonable to expect them to go through that again. Network Rail tried to argue that the scale of the works would be nothing like as great this time around.

Originally the plan was for the work to be complete when Thameslink was due to be complete. This is when it would be needed. Subsequently, when planning for the reconstruction of London Bridge was carried out in more detail, it was thought highly desirable to carry out these works as soon as possible to assist in maintaining reliability during these works. Because of this, the work was brought forward so that it would precede any timetable change consequent on the works at London Bridge. As the works would need to take advantage of a Christmas period for the necessary extended working, this meant that the bulk of the work had to be carried out in Christmas 2012.

The great irony of this that it looks like Thameslink will not now go to Dartford. True, under current tentative plans it will service Ashford, but this would not leave the main line so the question has to be made “Why do we need to double the flydown?” The answer appears to be given, for the first time ever, in a document published by Network Rail in May 2012.

Double tracking of the Tanners Hill fly down is required due to the removal of the Spa Road Junction, and to provide double junctions at both Tanners Hill Junction and Lewisham Vale Junctions with the main lines.

This is not really a complete answer, but it implies that the enhanced flydown is necessary because the new dedicated Thameslink tracks will make it impossible to cross the main line on the flat between London Bridge (Charing Cross platforms) and Lewisham. The trouble is that the document includes a diagram which seems to suggest that this will  be possible although it is hard to be sure as the bitmap diagram is of poor quality.

In part two we will look at the work that has been carried out since Easter 2012 culminating with a Christmas New Year blockade in order to achieve a double-tracked Tanners Hill Flydown.