https://en.wikipedia.org/wiki/List_of_equine_fatalities_in_the_Grand_National
Edit: I didn't realize that there are two ways to interpret the market title! Two horses died at the Grand National event weekend, but none in the Grand National race itself. It's (kind of) like whether non-combat deaths should be counted as casualties in war. I am sorry for this ambiguity in the question. I feel that the most fair way to resolve this is to resolve this N/A. I apologize for the lack of foresight; I didn't foresee the possibility of ambiguity. I also apologize to those who feel that this is the wrong way to handle the ambiguity, sincerely.
Edit: "Negative payouts too large for resolution. Contact admin." Ouch!
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A controversy has arose! I will let mods resolve on the 19th.
Edit: Actually unless the Mods feel strongly (or moderately strongly, but not lightly) otherwise, I'm inclined to resolve this N/A. There are two equally valid definitions of "at the Grand National".
@asmith I personally think N/A would be a better solution, 50% screws people who read the question the other way pretty badly. I should be able to re-resolve if you want
The "grand national" refers to the whole weekend, see e.g.
11-13 april
@draaglom Clear from the Wikipedia list cited it’s the race that’s being referred to, not the meeting.