the british rail class 206 or 3r was a type of diesel-electric multiple unit (demu) first created in 1964. they were re-formed from class 201 and class 416 vehicles for use on reading-redhill-tonbridge (north downs line) services. six three-car sets were created, numbered 1201–1206. they were nicknamed 'tadpole' units because of the contrast between the wide-bodied 416 'head' and the narrow-bodied 206 'tail'.