This is a badly worded question. If they mean a surviving husband, etc., the answer is probably �600,000, but it depends on whether the first deceased husband etc. left everything to their surviving partner or took the precaution of putting �300,000 into a nil rate band trust. If the latter is the case, the answer is �300,000, I think
Or if the husband etc. was the first to die and left everything to their partner, I assume there would be no IHT to pay. As this is not given as a choice I suppose one would have to opt for �1000,000, though I don't personally know of any limit. This question has been asked already, and one answer given goes into that question much more fully than I can.