I've been put in charge of making some modifications to a wordpress site, and one of the changes I need to make was to reduce the size of the banner on a particular page. I can see from the CSS that the height is defined by the style name "banner-top-main", and I can override this by customizing the theme and adding custom Additional CSS - but then it affects every single page in the site which isn't what is wanted. Does that really mean I'd have to somehow duplicate the whole theme and have just this one page use a different theme? Even then I'm not 100% sure how that would be done - by duplicating the template and selecting a different template? I've never really used wordpress to do this level of customization before and it's screaming out for a simple "edit page source" button where I can just go in and make the CSS and other changes I need for this single page, but I'm not seeing anything. I have googled extensively and not really found anything to help me, and I can't seem to get in contact with the original page designers (this is a volunteer job) so I'm resorting to asking newbie questions on stack-exchange sorry, hope I haven't just missed something embarrassingly obvious.
Thanks Dylan
P.S. I know I can do it by making use of the fact that each page has a separate class name for the body, e.g. page-id-580 in this case, but that seems a very flaky hack that's sure to cause issues when cloning/deploying the site changes between staging and live etc.