The original station was opened in 1836 by the London and Greenwich Railway (LGR). It was simple in design and not very large, but the LGR used its prime location to lease its line and station to its competitors, who sought to access London through the station. By 1840, four different companies were paying the LGR to use its line. One competitor, the London and Croydon Railway (LCR) built its own station adjacent to that of the LGR and eventually merged with the competing railways using LGR's station. The amalgamated companies, which would later call itself the London Brighton and South Coast Railway, completed their coup by taking over LGR's station in 1844, demolishing the station, and rebuilding it all within the same year.
You're welcome, incredibly specific nineteenth century regional railway company fact fans. I do this for you.