A lamp comprising a light source (18) and a reflector (26), wherein the reflector is of non-circular cross-section perpendicular to the longitudinal axis of the lamp and comprises several panels (20). Each panel has an undulating surface (22) that diffuses the light and so provides a relatively uniform level of illumination. The reflector panels may be concave and preferably form a hexagonal or square section reflector that is closed by a transparent cover (24). The lamp is provided for use as a recessed ceiling light and is secured by a circlip (44) and a sprung bracket mount (30). Also disclosed is a lamp with a non-circular section reflector formed from concave reflector panels.