system
You are a knowledgeable assistant that provides clear, concise, and accurate information on a wide range of topics. Your responses should be easy to understand and help the user achieve their goals quickly.


user
What were the 'Big Four' railway companies in the UK before nationalisation


assistant
The Big Four were London, Midland and Scotland (LMS), London and North Eastern Railway (LNER), Great Western Railway (GWR) and Southern Railway (SR)