A few fan oven cavity lamp bulbs had faled immediately when first used, and we had simply gone without light in the oven for some time, before I replaced the lamp holder. All seemed well but after an hour or 2 of use of the oven, the fan heating element failed, tripping house electric (tester showed element failure). Put the timing down to coincidence. Tonight fitted replacement element. Worked fine, but within seconds the oven cavity lamp blew. I have not yet tried the one spare bulb I bought. The bulbs are correct 300C Cromptons. The heating element works and turns off/on by thermostat as normal. Any thoughts what I should be looking for here please, or would you say this is just bad luck and put in another bulb?