I am publishing pages from my /docs folder as per https://github.com/blog/2228-simpler-github-pages-publishing
If I include this front matter on a page, the build breaks.
---
layout: page
title: "Help Page"
permalink: /help
---
The page is built but only contains the data from the <body> element. No headers, no stylesheet, just garbled HTML. The same occurs if I use layout: post.
If I removed the line layout: page then everything works.
According to the GitHub documentation - https://help.github.com/articles/configuring-jekyll/ - I should be able to use this frontmatter in my pages.
What blindingly obvious thing have I missed?

The "slate" theme only has a "default" layout.
So switching to
layout: defaultfixed the issues.