A lighting device (21), comprising a light source (21.1); a power controller (21.2; 21.20) configured to control the supply of electrical power to the light source (21.1) such that upon receipt of a start signal, the supplied electrical power is increased from a first value to a second value, the first value being different from zero and the second value being greater than the first value; and an input (21.4) for supplying the start signal.