What is List of railway companies involved in the 1923 grouping?
Under the [[Railways Act 1921]] the majority of the railway companies in Great Britain (along with a few in [[Northern Ireland]]) were grouped into four main companies, often termed the [[Big Four British railway companies|Big Four]]. The grouping took effect from 1 January 1923. ==The Big Four== <!-- This section is linked from January 1 --> The [[Big Four British railway companies|Big Four]] and their constituent companies, showing route mileage, were: *[[Great Western Railway]] (GWR) ** [[Great Western Railway]] {{convert|3005|mi|km}} ** [[Alexandra (Newport and South Wales) Docks and Railway]] (ADR) {{convert|10.5|mi|km}} ** [[Barry Railway]] (Barry) {{convert|68|mi|km}} ** [[Cambrian Railways]] (Cambrian) {{convert|295.25|mi|km}} ** [[Cardiff Railway]] (Cardiff) {{convert|11.75|mi|km}} ** [[Rhymney Railway]] (RhyR) {{convert|51|mi|km}} ** [[Taff Vale Railway]] (TVR) {{convert|124.5|mi|km}} *** for the list of subsidiary companies and joint railways see [[List of constituents of the Great Western Railway]] *[[London and North Eastern Railway]] (LNER) ** [[Great Central Railway]] (GCR) {{convert|852.5|mi|km}} ** [[Great Eastern Railway]] (GER) {{convert|1191.25|mi|km}} ** [[Great Northern Railway (Great Britain)|Great Northern Railway]] (GNR) {{convert|1051.25|mi|km}} ** [[Hull and Barnsley Railway]] (H&BR) {{convert|106.5|mi|km}} ** [[North Eastern Railway (UK)|North Eastern Railway]] (NER) {{convert|1757.75|mi|km}} ** [[Great North of Scotland Railway]] (GNSR) {{convert|334.5|mi|km}} ** [[North British Railway]] (NBR) {{convert|1378|mi|km}} *** for the list of subsidiary companies and joint railways see [[List of constituents of the London and North Eastern Railway]] *[[London, Midland and Scottish Railway]] (LMS) ** [[London and North Western Railway]] (LNWR); {{convert|2667.5|mi|km}} *** including [[Lancashire and Yorkshire Railway]] (L&YR) amalgamated from 1 January 1922 ** [[Furness Railway]] (Furness); {{convert|158|mi|km}} ** [[Midland Railway]] (MR) {{convert|2170.75|mi|km}} ** [[North Staffo