After the opening in 1836 of London Bridge station, the bridge had to contend with the extra crowds of City workers crossing it during the morning and evening rush hours. By the 1850s over a hundred thousand pedestrians used the bridge daily, and both the footpaths and the roadway were often extremely congested.The first suggestion that the bridge should be widened was put forward in 1854. The idea was to hang footpaths 12 feet wide over the sides of the bridge, though it would clearly not improve its architectural appearance. Similar proposals were made in 1869 and 1875, but they came to nothing, though it was clear that something had to be done. In 1882 plans were put forward for doubling the width of the bridge, but all such plans were put on hold when a new bridge at the Tower was proposed which, it was hoped, would ease the congestion.





More serious plans for the bridge's widening were discussed in 1900, when it was clear that, even after the construction of Tower Bridge, London Bridge was still unable to cope with the volume of traffic using it.The proposals met with much opposition, as it was felt by some that altering Rennie's bridge would severely damage the look of it, but work finally began in 1902. The operation involved cantilevering new footpaths out from the existing bridge, leaving room for a wider carriageway. The corbels and parapets were all of granite, to be in keeping with Rennie's structure. It was a complicated operation, as the bridge was kept open during the work, and temporary footbridges were put up on both sides.The new footpaths were declared fully open by the Lord Mayor in a ceremony at the end of March 1904.The work had cost ,£100,000 and was paid for by the Bridge House Estates.






By the 1960s Rennie's bridge could no longer cope with the demands placed on it. At first it was decided to widen the bridge again, but it was soon realized that it would have to be replaced by a more modern structure. The new bridge was designed by Harold Knox King, the City Engineer, with Lord Holford acting as architectural consultant, and Mott, Hay & Anderson as consulting engineers. The contractors were John Mowlem & Company, who tendered to build the bridge for just over £4 million. It is a three-arched cantilever bridge of pre-stressed concrete, clad in polished granite, and it is 100 feet wide, with a six-lane roadway. Work began in 1967 and lasted until 1972.There were complex problems to be solved in building the bridge, as it had to be on the same alignment as the old bridge, which had to be kept open during weekdays while the new bridge was being built.The solution was to build it in four sections, allowing pedestrians and traffic to use the rest of the bridge while each section was being constructed. The upstream quarter was built first, then the downstream section.The old bridge was then taken down so that the central sections could be constructed. Finally, all four sections were joined up and the surface added. All the work of construction and demolition was carried out using a massive gantry that rested on the piers of the old bridge. Each of the pre-cast units was hoisted into position and then suspended from the gantry until they could be joined up.The units are hollow, allowing essential services to cross the river - London Bridge is the only hollow bridge across the Thames. The downstream footpath was made considerably wider than the upstream one, as this is the side most used by commuters arriving at London Bridge station, and the footpaths are heated in winter. The new bridge was opened by the Queen on 16 March 1973, when she unveiled a plaque on the downstream parapet to commemorate the event.The bridge had taken 4,5 years to build and had cost £4.5 million, all of which came from the funds of the Bridge House Estates.