The London, Chatham and Dover railway brought passengers from Kent into London wanting to end up in both The City and the West End, and in Victorian times main line trains divided at Herne Hill, with portions headed in to Victoia (for the West End) and Holborn Viaduct (for the City). The result was short trains into Holborn Viaduct, where a site close by the Old Bailey and near to Bart's Hospital, Smithfield and St Paul's was 6 platforms wide but desparately short.
With the arrival of 8 car electric trains into Holborn Viaduct, platforms 1, 4 and 5 were - JUST - long enough if the trains pulled right up to the buffers, with platforms 2, 3 and 6 (latterly just 2 and 3) being used for parcels traffic. When that ceased the extra platforms were taken out leaving a great gap between 1 and 4.
The "Widened Lines", with traffic from the south past Blackfriars and Ludgate Hill plunged into a tunnel at Snow Hill then on through Farringdon and to King's Cross, closed to passenger traffic many moons ago, and at a later date to freight, and the tracks were pulled up. Then, many years later the tracks were renewed and through service re-commenced, calling at Snow Hill Station and leaving Holborn Viaduct on a spur which saw its final train on
29th January 1990.
I commuted in and out of Holborn from 1972 to 1976 and have a sort of love that comes from familiarity with the place. Sad to see it go, but that's tempered with the appreciation that it's been replaced which is something much better for the future.