Edit (0730 13/11/14): The site should now be back to normal. Sorry for any inconvenience to users of a mobile device.
In an attempt to track down the cause of excess CPU usage I will be disabling a number of WordPress plug-ins for a period of about 12 hours starting early this evening (12/11/14). During this time certain features will be lost, including comment preview, the Captcha and the mobile version of the site. It is also possible that some posts may appear in full on the home page rather than just the first paragraph of the preamble.