And I don't get the ultimatum. If you have money to split, why would you ask for more than half?
That one is a weird one. I think they need to seriously raise the amount you are dividing to have it make sense. I wouldn't care about what share of 50 pounds I was going to get as much as what share of 10 million I was going to get.
I picked 50% wondering who would ever pick anything else but then on a second read I understood it better. I initially thought each person splitting the money came up with a figure and they had to agree to get the money. Anything other than a 50/50 split wouldn't make much sense.
But the question is really that you get to put out a number, and the other person just gets to agree or disagree to take the remaining amount. Framed that way I guess it might make sense to try to angle for the slight advantage you've been given and pick a number that you feel the other party would agree to but that still gives you the better deal. Thing is, for 50 pounds I'm not going to try to get in the other guy's head over it. 10 million and maybe I try for an extra half a million or so.