Complex sentence: From 1924 Maunsell began standardising fleet of locomotives for ease of maintenance, whilst Bulleid undertook sweeping changes that propelled the Southern Railway into the forefront of locomotive design.
Split into simpler sentences: From 1924 Maunsell began standardising the fleet of locomotives for ease of maintenance. Later Bulleid undertook sweeping changes that propelled the Southern Railway into the forefront of locomotive design.