An electrical machine has a stator carrying electrical windings which protrude at opposite ends of the stator to form respective, ring-shaped end windings. The electrical machine further has a rotor having a plurality of magnetic field-producing elements for producing a rotor magnetic field which interacts with a stator magnetic field produced by the windings. The electrical machine further has a coolant bath for holding liquid coolant. The electrical machine further has a heat sink in thermal contact with at least one of the end windings, the bath and the heat sink being configured such that the heat sink is immersed in the coolant held in the bath. The heat sink defines one or more fluid pathways configured such that vapour bubbles, formed when coolant in contact with the heat sink boils, escape by rising through the heat sink.