Tonbridge

In 1937, at the SR’s Annual Meeting, the company proposed to electrify five routes, of which the extension of third rail from Sevenoaks to Hastings and Bexhill (West) was included. Completion of the necessary works were projected for January 1939. Electrification to Hastings was swiftly dropped on the basis that the route featured unusually narrow tunnels requiring the procurement of expensive tailor-made electric rolling stock. Just two years later, war with Germany broke out, and as a precaution, ‘’A’’ Box was enclosed from the windows downwards in a brick casing, to protect it against bomb blast damage. In 1941, the large area of vacant land in-between diverging Redhill and Sevenoaks routes was developed into a large marshalling yard to handle wartime freight traffic diverted away from London. The Redhill tracks were slewed southwards on a new alignment to accommodate the plethora of sidings, which produced a distinct kink in the original main line of 1842. A public footpath already existed across this field, and this was subsequently accommodated within the new yard development upon a 390-feet-long lattice footbridge spanning all tracks.

In November 1946, the SR announced a new electrification scheme involving six routes, two of which are of direct relevance to this section:

1. Sevenoaks to Ramsgate via Tonbridge, Ashford, Folkestone, Dover, and Deal
2. Tonbridge to West St Leonards, incorporating the Bexhill West branch

The company were overtaken in their proposals by nationalisation in 1948, but a similar electrification plan, albeit omitting the Hastings line, was pursued by British Railways. As part of ‘’Phase 2’’ of the Kent Coast Electrification Scheme, third rail was to be extended from its suburban limit at Sevenoaks to Dover, via Tonbridge, Ashford, and Folkestone. The Canterbury West branch to Ramsgate was also to be similarly treated, as were the Maidstone East to Ashford line and Folkestone Harbour branch. It was also intended to convert the engine shed at Tonbridge (Code 73J, formerly 74D) into a ‘’diesel garage and fuelling depot’’. In October 1960, construction of a new ‘’power box’’ commenced at Tonbridge, within the fork of the diverging Redhill line and West Yard freight sidings. Equipped with a push button route-setting panel, this was brought into use on 18th March 1962, initially controlling the Hildenborough to Tonbridge section of the Sevenoaks line. On 1 May of the same year, the panel’s scope was extended to Headcorn on the main line and to Yalding on the Medway Valley Line. Signalling at Headcorn was split between Tonbridge and Ashford Panels, these controlling the ‘’up’’ and ‘’down’’ loops at the station respectively. The mechanical cabins at Tonbridge were subsequently taken down and all semaphores replaced with four-aspect colour lights. The two berthing sidings on the ‘’down’’ side of the incoming Sevenoaks line were electrified, whilst those on the ‘’up’’ side of the station, parallel with the Redhill line, were retained but lacked third rail. Four sidings on the southern side of West Yard were also equipped with third rail for electric stock berthing. Electric working from Charing Cross to Dover, Ramsgate, and Maidstone West, via Tonbridge, commenced on 12th June 1961 under existing steam timings. A full diesel service between Charing Cross and Hastings via Tunbridge Wells had previously started on 9th June 1958. The full accelerated electric timetable on the main line came into use on 18th June 1962. Beyond Tonbridge, along the original trunk route to Redhill, mechanical signalling and steam-hauled services were retained. A diesel service along the Redhill line commenced on 4th January 1965, using ‘’Tadpole’’ units. Tonbridge engine shed had closed to steam in June of the previous year.

Mechanical signalling along the Tonbridge to Redhill line was finally replaced by colour lights in spring 1986, and control of the route was split between Three Bridges and Tonbridge Panels. The next wave of modernisation at Tonbridge was brought forward in conjunction with works relating to the Channel Tunnel. In spring 1990, the Government approved electrification of the Redhill to Tonbridge line to the tune of £19 million, primarily to allow the passage of Chunnel freight by an alternative route. In addition, quadruple track was to be laid along the first ¼-mile of the departing Sevenoaks line, and the curve of the route into the station eased. Advancements in signalling saw a new ‘’Integrated Electronic Control Centre’’ at Ashford take control of the main line in September 1993, superseding Tonbridge ‘’power box’’ on 27th of that month. The latter, however, remained to control the Hastings line. Diesel services between Tonbridge and Redhill ended in 1994, on completion of electrification, but the commencement of Chunnel freight over the line stalled. The Class 92 electric locomotives, procured specifically for the purpose of hauling such trains, started to fall foul to new signalling interference criteria. By summer 1996, a privatised ‘’Railtrack’’ had assumed control of former British Rail infrastructure, and was quick to put in place stringent regulations concerning interference between motive power and signalling equipment. Thus, Class 92s were banned from operating over the Wembley to Dollands Moor via Redhill route, which had been earmarked for them in the original Chunnel specification. The use of the line by ‘’Eurostar’’ services had been a non-starter from the outset, since limited clearances at East Croydon prevented the running of Trans Manche Super Train stock.

Final mention must now be made of the ‘’down’’ bay platform at Tonbridge, which for many years was dedicated to mail traffic. In 1995, a new rail-served platform to replace this facility came into use alongside Royal Mail’s huge sorting centre, ⅔-mile east of the station. This was commissioned as part of the modernisation of the mail by rail operation, which included the delivery of seventeen new Class 325 four-vehicle electric multiple units.

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