Is "historical" a word? Maybe in the UK? (In the US the word is "historic.")
Yes, it's a word on both sides of the ocean, two distinct usages. You use historical when you mean pertaining to history or having taken place in history. you use historic when you mean something important in the past.
I used the word historic and I've reported it because I think that it's accurate. I disagree with sherm0. I don't think that the use of historic and historical is distinct as described. When we use the word as a noun, (as is the case here), they are just almost synonymous. As an adjective, they are rather different. This is a historic event suggests importance. This is a historical event is more a statement of fact, i.e. that the occasion happened in the past, although the use off the word might suggest that the event is not without some significance. It is simply the case that it doesn't have to be.