* John Walker is known for the invention of the friction match in 1827. This is a significant invention, but it doesn't relate to building materials.
* London in 1832 was already a well-established city with a diverse range of building materials in use. At the time, common materials included brick, stone, wood, and even iron.
* It's unlikely a single person in 1832 would be credited with introducing a completely new building material to London. Building practices and materials evolved gradually over time.
It's possible the information you're looking for has been misremembered or is slightly inaccurate.
To help you find what you're looking for, could you please provide more context or any other information you have about this? For example:
* Is there a specific building in London you're interested in?
* Do you have any other details about John Walker, such as his occupation or any other known accomplishments?
* Are you sure it was 1832, or could it have been a different year?
With more information, I might be able to provide a more helpful answer!