CCE&HR south of Camden Town station allowing services to run from both City and West End branches to and from the Hampstead and Highgate branches. City branch services were extended to this station on 20 April 1924. The work required to join the two lines together at Camden Town was one of the most ambitious projects in the history of the Underground, and was undertaken without disrupting any existing services. It added another four tunnels that allows trains to proceed to or from either the Edgware or High Barnet branch on to or off both the City or Charing Cross branch without following conflicting paths. The multiple junction tunnels are effectively located beneath Camden High Street. The original lifts and emergency stairs to the platforms were inside the vertex of the V, leading to four passageways, one to each of the platforms, with return passageways back to the lifts. With growing patronage and increasing congestion the lifts were later replaced by escalators that came into service on 7 October 1929 with an escalator heading from the station building to a circulating area at the northern end of the platforms. This has only two pairs of parallel passageways, one for each branch (northbound), with a small side passage on each leading to the lower southbound platforms. One set of the original lift passageways became part of the ventilation system, but the remaining one adds to the confusion of the station. Northern line The line, known post-merger for many years as the 'Edgware - Morden' line, was formally referred to as the Northern line from 28 August 1937. The station was damaged by a bomb on 14 October 1940 during the Blitz. One person was killed. Shortly afterwards, Camden Town was chosen as one of eight stations on the Northern line where dedicated air-raid shelters would be constructed alongside the line, capable of accommodating 640,000 people. 2003 derailment On 19 October 2003, the last carriage of a 1995 stock train derailed on the approach to the station while traversing points in the connecting tunnels that connect the various Northern line branches. Seven passengers were injured, six of them with minor injuries. Two carriages were seriously damaged by the impact. After the accident, trains were restricted to travelling either from the Edgware branch to the Bank branch or from the High Barnet branch to the Charing Cross branch. Full use of the junction