I've inherited a site which has a module on the right hand side listing blogs, each of these is a sub category of a parent category called 'blogs'

The module is set to display every child of 'blogs' but I can't de-select one particular one which I want to hide.

I would normally just unpublish the blog but we'd like the content to stay online as it's getting great direct traffic from SEO, however that staff member has left and there was next to no traffic going to it from this module.

Where is the setting to hide that sub-category? I've looked in the category but can't see where to Hide it.

www.fespa.com/

Since you are referring to a module you will have to look under the Modules list. Just locate the Blogs module and filter the categories you want it to show.

"Categories List (Menu) Settings" is set to the parent category - "Blogs"

I've checked the module assignments and they don't seem to match the list of child categories being shown, but they do correspond to where the module is displayed.

Using K2 v 2.6.7

Let's short things out. You need to eliminate a sub-category from a module list, correct?
Is the module "Browse blogs" the one you need to change its items?

Yes and yes

OK. You have to go to Extensions -> Module Manager.
Locate Browse blogs module and through the Category filters under the Basic Options just select the categories you want it to fetch items from.

Under Basic options, I've got the following headings:

Archive settings

Authors List Settings

Calendar settings

Breadcrumbs settings

Categories List (Menu) Settings

Category Select Box Settings

Search Box Settings

Tag Cloud Settings

and

Custom Code Settings

Sorry, I still can't see where I should filter this? (I am a superadmin)

Oh, now I get it. The module you are using is the K2 Tools -> Categories List (Menu).
I'm afraid that you cannot set to leave a subcategory out through this module.
You can do it with css through.

Let's say that the sub-category you need to remove is the "LightWords Blog".
This sub-category is No7 in the list. Open your template's css file and add

.k2CategoriesListBlock ul li:nth-child(7) {display:none;}

Awesome

Thanks

You are welcome :)