The London Underground 1986 Tube Stock consisted of prototype electric multiple units that led to the development of the 1992 Stock. Two prototypes were built by Metro-Cammell, and the third by BREL (subsequently ABB, Adtranz, now Bombardier Transportation).
The (then) London Transport were looking to the future, so they contracted for three different prototype trains to be built.
Externally the trains were designed to the familiar core design for tube trains, but internally there were subtle differences (eg: the armrests, wrap-around windows, lighting, and more) and through a series of public consultations passengers were invited to comment on which they preferred. To make their identification easier the prototypes were distinctively and individually coloured - red, green and blue.
The public consultation results show that the BREL-built blue prototype was the favourite, and therefore the train provided the core design basis for the 1992 Stock.
The trains were used in service on the Jubilee Line until approximately 1989, when a derailment at Neasden resulted in the withdrawal of the stock. They also visited Woodford for a display on the Central line, and the Aldwych branch for an open day there. One car of the green train survives at the London Transport Museum's Acton Depot.