SharePoint 2013 Powershell: Exception calling "AddPublishingPage" with "2" argument(s): "Access is denied"

So, I'm trying to create pages via powershell, script below:

 # Get the SiteURL
 $SiteUrl = "https://MySiteCollectionURL"

 # Get the WebURL
 $WebUrl = "https://MyWebURL"

 # Get the PageLayout
 $PageLayoutRelUrl = "/_catalogs/masterpage/CustomPageLayout.aspx"

 # Get the Page URL
 $PageName = "Test.aspx"

 # Get the Title of the Page which is going to get created
 $PageTitle = "Test"

 # Initialize the Site Object
 $Site = Get-SPSite($SiteUrl)

 # Get the Publishing Site based on the SPSite
 $PubSite = New-Object Microsoft.SharePoint.Publishing.PublishingSite($Site)

 # Get the SPWeb Object
 $Web = Get-SPWeb $WebUrl

 # Initialize the PublishingWeb based on the SPWeb
 $PubWeb = [Microsoft.SharePoint.Publishing.PublishingWeb]::GetPublishingWeb($Web)

 # Get the PageLayouts Installed on the Publishing Site
 $Layouts = $PubSite.GetPageLayouts($False)

 # Get our PageLayout
 $PageLayout = $Layouts[$PageLayoutRelUrl]

 # Create a new publishing page.
 $Page = $PubWeb.AddPublishingPage($PageName, $PageLayout)

 # Assign the Title for the Page
 $Page.Title = $PageTitle

 # Update the Page
 $Page.Update();

 # Check in the Page with Comments
 $Page.CheckIn("Test Comment")

 # Publish the Page With Comments
 $Page.ListItem.File.Publish("Test Publish Comment")

Every time it gets to the AddPublishingPage command, it crashes out with the error:

Exception calling "AddPublishingPage" with "2" argument(s): "Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED))"

I have the 'shell window running as administrator, I'm a farm admin, and my account can create pages though the browser.

What gives?