ETA 14/3/2012: The problem has no been resolved -- please see next news item.
Original news item:
We are aware of a problem that seems to have begun early this morning (GMT) where people trying to reach the site with their Android devices -- tablets and smartphones -- are being redirected to a Russian porn site.
We are both currently in our respective workplaces, and will look into it properly as soon as we can tonight.
In the meantime, if you are able to switch your 'user agent' in your browser from mobile or custom to 'desktop' this appears to prevent the redirect from occurring. To do this you will need to go into the browser and then into the settings.
Redirected mobile users