You (and AC) got that wrong.
In the UK, the person who is alleged to have committed the libel must prove their case. So, if the NewsOfTheWorld alleges that a well-known Scottish MSP is a fornicating baboon, and said baboon sues the NOTW for libel, the NOTW must then *prove* that said baboon has fornicated inappropriately. This can be difficult, but you might reasonably say that if the NOTW can't prove its case then it shouldn't have printed the story in the first place. Said baboon is, for current purposes, innocent until proven guilty, although that's not really relevant in libel.
In the US, the situation is very different. If I call someone a paedophile in print, and he sues me, then *he* has to prove that he *isn't* a paedophile. Which is in general, of course, impossible, so I can say pretty much what I want and get away with it. This is justified in the name of "Free Speech".
Which is all very interesting, because many people, particularly those who have different libel laws, are of the opinion that British libel laws suppress Free Speech. I personally am of the opinion that these people are just a little bit Thick, but YMMV.