In 1984, London Transport ordered three different prototype trains to test new materials, construction methods and seating layouts.

[1] Two were built by Metro-Cammell at its Washwood Heath factory, and the third by British Rail Engineering Limited at its Derby Litchurch Lane Works.

All were built to the same design and were able to operate in four, six or eight car formations, despite each set having different electrical equipment supplied by different manufacturers.

[4] To make their identification easier the prototypes were distinctively and individually coloured - red, blue and green.

Afterwards the latter was stored at Ash Grove bus garage before moving to the London Transport Museum's Acton depot.