Sophos for Microsoft SharePoint: 'Virus Scanner update' shows as failed

Issue
When you check in SharePoint|Central Administration|Operations|Timer Job Status, the 'Virus Scanner Update' shows a status of 'Failed', despite the fact that Sophos Anti-Virus has successfully updated.

Sophos product and version
Sophos for Microsoft SharePoint

What to do

1. Go to Windows Services and start the 'Windows SharePoint Services Administration' service.
2. Wait for several minutes, then re-check the status of the 'Virus Scanner Update'. It should now display a status of 'Succeeded'.

Note: This issue arises as a result of the SharePoint update job functionality, and is unconnected to Sophos AutoUpdate.