User Role to edit single page

Hello. (posting here too as I think I’ve posted in the wrong place. Please accept my apologies)

I’ve built a site for a client, only ten pages, nothing especially big, and created a role for them called Blogger, as the staff need to be able to both blog and access a couple of plugins (for a client carousel and to add testimonials). I disabled their ability to edit pages using a plugin called Adminimise as I didn’t really want to give them that access and break anything by mistake.

OK – All is well so far? This is where I’ve discovered Adminimise falls short. What my client requires is that just one page-a page called Trustees- is editable by them so they can add names as required.

How can I make an individual page editable by a non-administrative role whilst disabling the others? I’m praying this is possible, but am not getting very far with Google.

Thanks for reading/responding

Andy