Well, I think direct evidence is tricky. He was never going to be able to say ‘Journalist X listened to this voicemail at this time on this day’.
Personally I would have thought he needs to be able to say, convincingly, that he recalls leaving or receiving voicemail messages on the matters relevant to the article, to at least raise the possibility that the voicemail messages were the source of the articles he complains of. But he’s not done that at all - he even backed away from the question when directly asked if he might have left a voicemail describing Paul Burrell in the same terms that was used in an article.
Rooney couldn’t show any direct contact between Vardy or her agent and the journalist, but things like the random loss of the agent’s phone into the sea, Vardy’s ‘broken’ laptop, the no-show of the agent in court was the sort of circumstantial evidence that, taken together with everything else, persuaded the judge that in the balance of probabilities, they had done what they were accused of.
Even with a lot of the WhatsApp messages from both Vardy and her agent “mysteriously” being unable to be disclosed, there was still plenty of direct (and damning) messages between them to show what was happening. Eg Vardy texting her agent with a titbit about a footballer and saying “I’ll want paying for this” and another time her agent saying in relation to Colleen asking who would share information that “It was me!”. And, as has pointed out, complete lack of another source for the stories in the Vardy. That’s not the case here, as the KC has been painstakingly pointing out.