1st Lothians and Border Yeomanry
2nd Lothians and Border Horse
In the 1930s, it was mechanised and became a unit of the Royal Armoured Corps.
Due to the poor availability of armoured vehicles and tanks at the start of the Second World War, some units were formed to create Motor Machine Gun Brigades. This unit joined the 1st MMG Bde on 12 June 1940 and remained with it under reorganised as the 26th Armoured Brigade on 12 October 1940.