A heat engine comprising: an expander; a recuperator; a heater; a fluid pump; a working-fluid path including a high-pressure path for communicating pumped working fluid from the fluid pump toward the expander on a high-pressure side, and a low-pressure path for communicating the expanded working fluid away from the expander on a low-pressure side, the heat engine using a condensable working fluid, which, at least in part of the high-pressure path, is in the liquid phase, the high-pressure path at least extending between the recuperator and the expander via the heater, and the low-pressure path at least extending between expander and the recuperator; characterised in that it further comprises a fluid-drainage path extending between a first connection point on the high-pressure path and a second connection point on the low-pressure path, the fluid drainage path being selectably open or closed for selectively draining working fluid from the high-pressure side toward the low-pressure side, a first portion of the fluid drainage path being connected to a portion of the high-pressure path, in which during normal operation the working fluid is mainly in the liquid phase, at the first connection point, the first connection point being located on the high pressure path downstream of the fluid pump and further located on the high pressure path between the recuperator and the heater, and a second portion of the fluid-drainage path being connected to the low-pressure path at the second connection point, the second connection point being located on the low-pressure path between the expander and the recuperator. an expander; a recuperator; a heater; a fluid pump; a working-fluid path including a high-pressure path for communicating pumped working fluid from the fluid pump toward the expander on a high-pressure side, and a low-pressure path for communicating the expanded working fluid away from the expander on a low-pressure side, the heat engine using a condensable working fluid, which, at least in part of the high-pressure path, is in the liquid phase, the high-pressure path at least extending between the recuperator and the expander via the heater, and the low-pressure path at least extending between expander and the recuperator; characterised in that it further comprises a fluid-drainage path extending between a first connection point on the high-pressure path and a second connection point on the low-pressure path, the fluid drainage path being selectably open or closed for selectively draining working fluid from the high-pressure side toward the low-pressure side, a first portion of the fluid drainage path being connected to a portion of the high-pressure path, in which during normal operation the working fluid is mainly in the liquid phase, at the first connection point, the first connection point being located on the high pressure path downstream of the fluid pump and further located on the high pressure path between the recuperator and the heater, and a second portion of the fluid-drainage path being connected to the low-pressure path at the second connection point, the second connection point being located on the low-pressure path between the expander and the recuperator.