[Source: Nick Catford]
A 1950s track and signalling diagram with subsequent details added. North is to the left and south to the right, with the Westerham branch heading away westwards at the bottom. Dunton Green signal box was midway between Polhill and Sevenoaks No.1 boxes. Much of the Dunton Green diagram is self-explanatory but a few details are worth a mention. Towards top right Wreford's Siding can be seen with its gate represented by the truncheon-like symbol. As the text explains, the points were operated via a ground frame electrically released from the signal box. This means the down starting signals would have to be set to danger before the signalman could release the ground frame and also the trap points within the siding (both marked 'x'). With a train in the siding and clear of the trap points, the points would be reset and locked. The procedure would then be repeated when the train was ready to depart. It should be noted that signalling diagrams are in schematic form and sidings as shown may not, usually did not, represent their true length. At the bottom centre of the diagram is explained the lifting, reinstatement and final lifting of the track through the branch platform together with the goods sidings and the points from the main line. The siding marked 'Dead End' was the trap siding protecting the up main from the branch. The crossover between up and down main lines is visible in a number of images and its main use would have been for locomotives and stock leaving the branch to return to Tonbridge. It is thought that at one time another crossover existed north of the station allowing access from down main to branch but it is not known if this was in addition to, or was replaced by, the crossover seen on the above diagram. Distant signals are shown with the usual 'notched arm' symbol with shunt signals shown as marked, for example, at D, E, F and G. Some signals can be seen with a diamond symbol on their posts. This represents track circuiting, the passing of an electric current through the rails which, when short-circuited by the wheels and axles of a train, inform signalmen of the train's presence via
instruments in the signal box.