These are not well known, if only because so few people visit the Royal Exchange today, but they are a notable sequence, which belong to the Victorian history of public art that includes the major Westminster sequence and Madox Brown's efforts in Manchester Town Hall.
The London series relates episodes from the City's history (naturally) with some excursions beyond the walls, including the opening panel (top) of Phoenicians trading in Cornwall by Frederic Leighton, and another featuring Magna Carta at Runnymede.
Two by Stanhope Forbes - citizenry taking to the Thames during the Great Fire, and the gutting of the previous Exchange in 1838 - are worth being seen, both for their shared fiery scenes and for their visually effective compositions for tall works to be viewed from the floor.
I'm not sure of the murals' own history except that they must have been projected in the 1890s and continued through to the 1920s, as the later panels feature the Great War. The list of artists is a roll-call of eminent and now mostly forgotten late Victorians.
More on Kemp Welch's work http://spitalfieldslife.com/
The proposals are for a mezzanine floor halfway up the paintings, obscuring their central sections and frankly making nonsense of the images. A mock-up of the predicted effect below.
Here is where to register an objection. Here is the VicSoc's fully itemised objection, which covers more than just the paintings. And here is the full sequence of images, courtesy SpitalfieldsLife