A rare 1937 ‘Quad Royal’ Beck poster map of the London Underground

A rare example of the largest format tube map, published only four years after the introduction of Henry Beck's iconic 'electric circuit' diagram. It exhibits some of the short-lived 'innovations' forced on Beck by his superiors: there are large white diamonds containing the names of the interchange stations; the lines have been thickened to accommodate the line names in white; and small black diamonds mark the main line termini. The map also marks a period of intense building work, showing the under construction extensions on the Central London Line, Bakerloo and Northern Line, including the cancelled link between the Barnet and Edware branches and the spur to Alexandra Palace. The issue code is 36.3962.2500.