King William Street Stations construction was difficult with regular subsidence due to the water-logged ground around the river but the tunnel and station were eventually completed on 4th November 1890 and the public service commencing on 18th December. The then Prince of Wales did the honour of opening the line.
The new line was heavily used from the opening day and the station layout quickly proved unsatisfactory. To overcome this, a Bill was introduced into Parliament in 1882 to construct a new line from Borough to Moorgate Street and abandon the unsuitable terminus. The Bill received Royal Ascent in 1883 but this was for a long term solution. To alleviate the congestion problems in the short term, surface facilities were improved by taking a lease on an existing building in Arthur Street East for a Ladies Room, Parcels Room and Left Luggage Office. A plan to install a third lift was dropped because of cost.
With 15,000 passengers using the station daily, improvements were also urgently required at platform level so the single line was replaced by twin lines running into an island platform which was completed by December 1895. A scissors crossing was added at the south end allowing trains to use either line but this required a shortening of the platform which could now only be used by three car trains.
February 1900; the station and the tunnels running under the Thames to Borough were abandoned. Initially no use was found for the tunnels but as early as 1901 it was suggested they could be used for cultivating mushrooms or as a bonded store. The favoured solution was to use the tunnels to carry telephone or electric cables but no user could be found. Initially the track remained in place and was used to store empty stock.
In later years it was used as an air raid shelter.