Complex sentence: The first standard-gauge examples were Robert Harben Whitelegg's design for the London, Tilbury and Southend Railway in 1912, although not delivered until after the LT&SR had been taken over by the Midland Railway, where they were the 2100 class.
Split into simpler sentences: The first standard-gauge examples were Robert Whitelegg's design in 1912 for the London, Tilbury and Southend Railway (LT&SR). They were only delivered after the LT&SR had been taken over by the Midland Railway, where they were designated the 2100 class.