According to that Sunday Mirror "interview" with him you posted, he obviously admitted to his crimes, no? But then he decided to vehemently deny them?
Also, kids they interviewed in the same article later came forward saying that they were paid by the tabloid to lie about it. Sri Lankan police which investigated the whole thing and interviewed same boys found the accusations to be baseless.
Not to mention Clarke was 80 years at the time of accusation, and was bound to a wheelchair, not exactly a likely candidate for what he was being accused of.
I don't know what else could possibly anyone do to prove they're not guilty of something like this once they're accused, and if you follow your logic, you'll always think everyone is guilty of something like this if a tabloid accuses them, no matter what the eventual outcome, and their defense is.