What if, and I know its a stretch, Edward Oxford had managed to kill both Prince Albert and Queen Victoria in 1840? None of her children would have been born, (Victoria was born in November of 1840, the attempt took place in June) and since her predecessor had no heirs, I think it would pass to Ernest Augustus of Hanover, and then, when he dies, his son George the Fifth, ( http://en.wikipedia.org/wiki/George_V_of_Hanover ) would take control. I may be wrong about the succession, but what would the overall effects of the assassination be?