Why is there a cluster of tall buildings in the City of London?
It's partly because the City of London isn't averse to highrise development, but mainly because tall buildings are allowed to be built in some locations and not others.
For a full explanation you should read the 32 page planning document Tall Buildings in the City of London published in March 2019. I have, and I shall now oversimplify its contents for those of you with limited time. In short it's all about St Paul's Cathedral, but also to a lesser extent the Monument and the Tower of London.
For centuries the only tall buildings in the City were churches. In the 1930s the construction of a (gasp) 11 storeybuilding caused consternation when it blocked views of St Paul's Cathedral from the Thames riverside. In response the City Corporation introduced a local view protection policy called the St Paul's Heights. This successfully kept highrise development at bay until the 1960s.
The St Paul's Heights plan was intended to protect local views of the cathedral from the South Bank, the Thames bridges (including Waterloo Bridge and London Bridge) and along certain key streets (such as Fleet Street). My map shows the affected area in orange. Views from the South Bank and bridges explain most of the large chunk nearest to the river, while three streets in Islington (Farringdon Road, Amwell Street and St John Street) account for the sector to the north. Maximum heights were calculated for individual grid squares across the entire zone (for example in the Smithfield area no building can exceed 52m). The St Paul's Heights plan remains in force.
In 1991 the government defined eight Strategic Views to protect sight of the dome of St Paul's Cathedral from more distant viewpoints. The eight chosen locations were:
» Greenwich Park and Blackheath Point in southeast London
» Primrose Hill, Parliament Hill, Kenwood and Alexandra Palace to the north
» Richmond Park and Westminster Pier to the southwest
The reason you can only see five sectors on the map, not eight, is that some of the corridors have merged before they reach the boundaries of the City.
Strategic Views were later devolved to the Mayor of London. In 2007 Ken Livingstone narrowed their width and renamed them Protected Vistas. In 2010 Boris Johnson widened them again as a compromise between the two previous widths. The London View Management Framework remains in force.
The Monument Views Policy Area protects and enhances views of and from the Monument. It includes the four street blocks surrounding the Monument, plus five protected views from the viewing gallery itself (towards the Tower, the Thames, London Bridge, Waterloo Bridge and St Paul's). It's shown above in green.
Meanwhile in yellow is an area to protect the silhouette of the Tower of London, specifically the White Tower, as seen from the opposite side of the Thames. World Heritage Site skylines must be preserved.
Lines of sight prohibit the construction of tall buildings in all of these areas - orange, red, green and yellow. But there's one more factor to take into account...
This is a map of the City's 27 Conservation Areas. The first was designated in 1971 and the most recent (the Golden Lane Estate and Barbican Estate) in 2018. Official policy is that the development of a tall building in a Conservation Area would be inappropriate, so no new ones are permitted. Light-coloured areas on the map show that the City isn't as chock-full with historic buildings as some might think - a lot is covered by generic demolishable office blocks.
As you can see, most of the Square Mile has been blotted out leaving only a few areas suitable for highrise development. One is west of St Paul's around Fetter Lane. A larger patch spreads from London Wall down to Cheapside. A significant chunk is up north around Liverpool Street station. But the largest area of land available for tall buildings is to the east of Bishopsgate around Fenchurch Street and Leadenhall. This is where most of the whoppers have ended up, forming the so-called Eastern Cluster.
This final map shows the actual location of City buildings over 75m in height.
Light blue buildings precede 1970 - they're mostly churches. Red and yellow cover the rest of the 20th century, including the Barbican and Nat West Tower. Green brings us into the 2000s, including the Gherkin and the Broadgate Tower. Dark blue covers the last decade, confirming that construction has been speeding up recently. Empty circles show tall buildings under construction or not yet begun.
At present more than 60 City buildings exceed 75m in height and nine exceed 150m. Several more are on the drawing board. Most of the new batch are located inside an approximate triangle bounded by Liverpool Street station, Fenchurch Street station and Leadenhall Market. None are targeted for the western half of the City, nor anywhere near the river.
I've skated over all this, so if you're really interested you should read the full report. You may not like how high the City of London is climbing, nor how fast, but you can at least take comfort that tall buildings can't be built just anywhere... and we have St Paul's Cathedral to thank for that.