A modifying structure lens 1 is formed over a LED light source 2 so as to act to focus the light into the appropriate configuration ray direction and simultaneously extract heat from the upper and side surface of the LED chip 2. The LED light source 2 is mounted to a rear heat sink body 4. The lens 1 comprises a primary region 5 immediately adjacent the LED source 2 and within which the LED source 2 is embedded. The primary region 5 includes a diamond compound particulate material distributed throughout a flexible gel matrix, as will be described in detail hereafter. An overlaying layer 6 of a light transparent material is not impregnated with the diamond compound material.
