A First Open or FO, is a type of railway carriage used by British Rail. They were first produced as British Railways Mark 1

British Railways Mark 1

British Railways Mark 1 was the family designation for the first standardised designs of railway carriages built by British Railways. Following nationalisation in 1948, BR had continued to build carriages to the designs of the "Big Four" companies , and the Mark 1 was intended to be the...

, and subsequently Mark 2

British Rail Mark 2

The Mark 2 family of railway carriages were British Rail's second design of carriages. They were built by British Rail workshops between 1964 and 1975...

, Mark 3

British Rail Mark 3

British Rail's third design of standard carriage was designated 'Mark 3' , and was developed primarily for the InterCity 125 High Speed Train...

, and Mark 4

British Rail Mark 4

British Rail's fourth design of passenger carriages was designated Mark 4, designed for use in InterCity 225 sets on the newly-electrified East Coast Main Line between London, Leeds, and Edinburgh.-History and construction:...

 variants were produced.

Mark 4

Built in 1988 by Metro Cammell

Metro Cammell

The Metropolitan Cammell Carriage and Wagon Company was a Birmingham, England based manufacturer of railway carriages and wagons, based in Saltley and subsequently Washwood Heath....

 at their Washwood Heath plant in Birmingham, the coaches are 23 m long with power operated sliding plug door

Plug door

A plug door is a door designed to seal itself by taking advantage of pressure difference on its two sides and is typically used on pressurised aircraft...

s, are fitted with SIG bogies and are capable of running at up to 140 mph (225 km/h) but usually run at a maximum of 125 mph (200 km/h).