Complex sentence: Designed for and largely operated in London, over 2,800 AEC Routemasters were built between 1956 and 1968, with a design so robust that the Routemaster outlasted newer buses intended to replace it, remaining in use until 2005, well into the deregulated era.
Split into simpler sentences: Designed for and largely operated in London, over 2,800 AEC Routemasters were built between 1956 and 1968. So robust was the design that the Routemaster outlasted newer buses intended to replace it, and remained in use until 2005, well into the deregulated era.