How important is the Oxford HAT for the application process?

Hey everyone, first time I am asking a question! I want to apply to Oxford in order to study history there and, in order to do so, I have to sit the HAT. However, due to a school trip going on at the same time, I am having to sit my test in the US...which will probably affect my performance. I am wondering how important the HAT is compared to the other parts of the app process and whether Oxford can be informed of any special circumstances surrounding the sitting of the HAT. Thanks!

The HAT is very important in admissions, as it usually determines whether or not you'll be invited to interview. If you do badly in the HAT, then, you can't make up for it later on. They do take extenuating circumstances into account, but this might not qualify. There's some more information here:
https://support.admissionstesting.org/hc/en-gb/articles/205628475