british rail class 23, originally called english electric type 2, was a class of ten diesel-electric locomotives built by the english electric company in 1959. they were numbered from d5900 to d5909. the power unit was a napier deltic t9-29 9 cylinder engine of 1,100 bhp. this drove an ee generator, which powered the four traction motors. the class 23 was nicknamed "baby deltic" because of its similarity to the class 55.