Hide Overflow on a Specific WordPress Template

This:

html .page-template-showreel-php {
    overflow: hidden;
    }

…will target body.page-template-showreel-php. So, two questions:

  1. Do you have the <?php body_class(); ?> template tag inside of the <body> HTML tag?
  2. Is hiding overflow on the <body> tag really what you’re after, or do you need to target a descendant element?

EDIT

There is no semantic or programmatic reason that you can’t re-use the <?php body_class(); ?> template tag inside the <html> tag also. So, you might consider:

<html <?php body_class(); ?>>

and then:

html.page-template-showreel-php {
    overflow: hidden;
}

Worth a shot…