Safari white box with blue question mark
I got a MacBook with latest Sierra 10.12.1 and all off a sudden all I see is a white box with blue question mark on https://www.theguardian.com/uk site instead of pictures using Safari. Pictures are showing ok on Firefox, under a different login-in on the same Mac and for other news sites whilst using Safari so the issue must be with my Safari settings with the theguardian site.
I've removed all plug-ins and extensions (none were theguardian specific anyway), emptied the cache and disabled extensions in the develop dropdown. Any advise on what to try next?
I'm prepared to do a factory default reset to clear this but even this is not available. Thanks
MacBook Pro (Retina, 13-inch, Mid 2014), iOS 10.1