A hydrogen generator comprising an enclosure, a series of spaced plates contained within the enclosure and defining between them liquidtight cells, with a plate forming a first wall of each cell of a nobler material than a plate forming a second wall of that cell, and where a first place of the series is an anode arranged to be connected to a power supply and the last plate of the series is a cathode arranged to be connected to a power supply, an inlet to each cell arranged to allow an electrolyte to flow into the cell, and an outlet from each cell arranged to allow an electrolyte and hydrogen gas to flow out of the cell.