A lamp includes a discharge vessel; electrodes spaced apart in the discharge vessel comprising tungsten or tungsten alloy; and a fill sealed within the vessel having a pressure between 50-200 mbar. The fill includes: a starting gas which comprises: xenon, krypton, argon or combinations thereof with the exception of pure argon; optionally radioactive Kr85 with a maximum activity level of 0.124 MBq/l as part of the starting gas; and a metal halide component. The lamp includes an active tungsten regeneration cycle wherein the fill comprises a species of the tungsten or tungsten alloy of material of the electrodes during lamp operation, wherein the solubility of tungsten or components of tungsten alloy in the tungsten or tungsten alloy species is lower in a gas phase adjacent to the electrodes than at close proximity of the wall of the discharge vessel.