Hide a div on a single post but its hardcoded

I know this will seem like a strange request but I do have a reason why I am working the way I am.

I have a div on every page at the top of my site and it is in the template header, this div contains an affiliate banner as I needed this to show on every page.

I have one post that is related to a charity and is really a human interest post I dont want to distract from this by having my adverts or banners up on that page but I do need them up on the other 100+ pages of the site as I need to make money but I do want to really give my absolute support to the charity (Ideally I would like to swap out the banner I have for an affiliate for their banner but it would be okay if I could just remove mine).

I am quite useful with wordpress and have a basic understanding of html, I can get by with css but its not something I am good at, it scares me….

The best option I can see is to hide the div contents on the one post as having an empty space their does work well with the post content and look but I am not sure how to do this.

Can anyone help me out, i cant have a human interest post for a charity with an affiliate banner across the top of the page, it makes me look like a terrible person!?

Thanks