The British Rail Class 126 diesel multiple unit was built by BR Swindon Works in 1959/60 to work services from Glasgow to Ayrshire and comprised 22 3-car sets and were a development of the earlier Swindon-built trainsets that had been introduced in 1955 to work the Edinburgh Waverley - Glasgow Queen St services. These vehicles formed the first Inter City service to be operated by diesel units in Great Britain.

The introduction of these early diesel multiple units originated in a British Transport Commission report of 1952 that suggested the trial use of diesel railcars. BR's Swindon Works were chosen to design and build express units for the ex-North British Railway Edinburgh Waverley to Glasgow Queen Street route.

4 vehicles survive