If a diesel multiple unit is a DMU, and an electric multiple unit is an EMU, then this must be a HMU! Hydrogen fuel cell powered 799201 leaves Long Marston on 9 February 2023 with the 5Q98 11:29 Long Marston to Evesham West Junction test run. This is the second Class 799 conversion, being the former dual voltage EMU 319382, which has been fitted with a Ballard FCveloCity unit, allowing it to run on non-electrified lines.