The reporting has changed about age which was not said when I raised the topic.
I agree, no excuse or defense now.
However the law is ass
From the CPS- Making indecent images can have a wide definition in the law and can include opening an email attachment containing such an image, downloading one from a website, or receiving one via social media, even if unsolicited and even if part of a group."
So you friend can send you an image, you can completely and legitimately ignorant that the content is illegal, thinking the person is of age and that's it doomed.