The British Rail Class 204 designation has been used twice for two similar types of diesel-electric multiple units.

In 1979, BR decided to augment the two-car units to three-car formation.

The Class 204 designation was re-applied to these four newly formed units (which were also given the classification 3T under the old system).

In 1986, the units were renumbered to 204001-004 to conform with the TOPS numbering system.

Power car (one per set) Original Class 204 (2H) Units Reformed Class 204 (3T) Units * ex-Class 205 Of the original 2H units, a single driving trailer has been preserved.