Same problem, and I've been having the same issue with other sites.
It's the after effects of Global Signs major screw up a couple of days ago [1]. They managed to revoke one of their own cross-signing certificates by mistake. We'll be seeing problems like this for a few more days until cache clears.
Works fine here.
The certificate I’m getting (49 f4 d4 f3 ca df 0a 4a 5a 54 f4 90) is issued to i.ssl.fastly.net and has 152 other alternative names, including
DNS Name=theguardian.com
DNS Name=*.theguardian.com
I am seeing it. I can't see the images on Safari either, they show broken. It is saying the certificate was revoked.