They had non-standard equipment that precluded multiple-unit operation with any other type of train, and had significantly more powerful motors which resulted in acceleration of 1.5 miles per hour per second (2.4 km/(h⋅s)) (which was considerably better than existing District Railway rolling stock).

[1] This was a less-than-ideal design, because it limited the driver's forward view in what is now considered a cramped, ergonomically unfriendly cab.

[2] As built, the initial design of the stock was unwelcoming with a cold steel appearance, seats covered in a Rexine-type material and roof-to-floor grab-poles for standing commuters.

Frank Pick, the innovator of so much change on the Underground system, commissioned a well-known artist who improved the appearance of the upholstery, supplied armrests between individual seats, and replaced the grab-poles with hanging straps.

Some four-car sets also worked the East London Line during the 1950s with maintenance being undertaken at Neasden depot.