 When originally planned by the GN & SR , Holborn station was to have just two platforms . The first GNP & BR plan for the station would have seen the two platforms shared by trains on the main route and by the shuttle service on the branch with the junctions between the tunnels south of the station . The interference that shuttle trains would have caused to services on the main route led to a redesign so that two northbound platforms were provided , one for the main line and one for the branch line , with a single southbound platform . The junctions between the two northbound tunnels would have been 75 metres ( 246 ft ) north of the platforms . When powers were sought to build the junction in 1905 , the layout was changed again so that four platforms were to be provided . The southbound tunnel of the main route no longer connected to the branch , which was to be provided with an additional platform in a dead @-@ end tunnel accessed from a crossover from the northbound branch tunnel . As built , for ease of passenger access , the branch 's northbound tunnel ended in a dead @-@ end platform adjacent to the northbound main line platform with the branch 's southbound tunnel connected to the northbound main line tunnel . To enable the southbound tunnel of the main route to avoid the branch tunnels , it was constructed at a lower level than the other tunnels and platforms . The tunnel towards Covent Garden ( at this point heading south @-@ west ) passes under the branch tunnels . 
