- title(page_heading) unless content_for?(:page_title)
%h1#page-h1.heading-xlarge
  = page_heading

- title(page_heading) unless content_for?(:page_title)
%h1#page-h1.govuk-heading-xl
  = page_heading

Replace class heading-xlarge with govuk-heading-xl
Replace class heading-xlarge with govuk-heading-xl
