Link to the page not the homepage on TNA for a 404

We currently link to the TNA page for the domain, rather than the TNA page for the page you requested. When this behaviour was originally chosen, the assumption may have been that the page probably isn't in the archive, so linking to the archive for the homepage was a better option.

If I am correct about the origins of this behaviour, then it may have been when we thought our coverage would be excellent. That is not generally the case.
Should `request.host` just be `host` here?