Old London Bridge
The vast majority of my new series will be set in and around the old City of London. The City was situated on the north bank of the River Thames, between Blackfriars to the west and the Tower of London to the east. The seat of power, where the monarch lived, and where his government sat, were further west outside the City walls, in Westminster and Whitehall.
At the time of the series, London Bridge was the only river crossing in London, and it ran from an area near the Tower of London, to Southwark, a less populated but rapidly expanding suburb. A bridge was necessary, not only for those living in Southwark, but also for merchants, traders and travellers from the south who needed access to the bustling markets and businesses of the City.
The bridge was more than just a bridge, however. It was lined with shops and houses, and at its peak was home to about 1000 people at any one time. Often homes were just rooms in larger buildings that were built precariously on either side of the bridge. This left little room between the buildings for people to actually use it as a crossing. In many parts it was impossible to see the river.
You can see more details in the first two images below. Looking at the top image, it would seem that living on the bridge was not for the faint hearted, and certainly not for those with vertigo!

The second image shows the bridge, but also has part of the old City in the background. Images of both the bridge and the City are often used on the covers of books of this time period. The reason I became interested in it.
New London Bridge
By the 1820s the old bridge was no longer fit for purse. The narrow passageway between the houses was insufficient for the ever increasing traffic, and the arches beneath the bridge had become a barrier to shipping needing to get up to Westminster and beyond.
The demolition was completed by 1831, while a replacement stone bridge was built a little further up river. This structure lasted for 140 years, before it too needed replacing.
The current bridge (pictured below) was opened to traffic in 1973. You can see that it now has no real distinguishing features. A shame for those who look back on history with nostalgia, but probably very welcome by those who need to cross the river!

Further Reading:
https://www.londonmuseum.org.uk/collections/london-stories/london-bridge/
https://themindcircle.com/lesser-known-architectural-wonders/