THAT'S IT! I'm convinced now. If you look very closely (replay it repeatedly) you can see the last ball actually rise up slightly immediately after Derren announces ball number 23, at 2:04.
I can think of several ways to do this - none of which match with whats seen though.
Notice that in the spiel before hand he says that after the meeting with Camelot that the BBC have the rights to
announce the results.
i.e. DB goes to Camelot and explans what he wants to do and Camelot say - well as you are predicting nothing and simply cleverly announcing what the result is after the fact, you can't do that cos of "legal reasons"
If the clever printer angle was used then why no studio audience? Such a device would have been able to be watched from all angles, so he'd likely have bussed in an audience to make things look more convincing.
At the start he claims there is only him and 2 cameramen, 1 of those cameramen gets used twice only(!) and what about soundmen or the person whispering into his earpiece when he can turn the TV on?
The trick must involve some method of either marking the balls in the 25secs or so he has after they come out of the machine to when he reveals his balls (ooer missus) - or switching the balls with correctly marked ones after the draw. He also never shows us that whats in the rack at the start of the show are infact balls, they are never touched or examined by anyone prior to the reveal. Tho close analysis of them shows the one at the end jumps, very shortly after some (intentional?) camera wobble, a little.
Other oddities. The back of the card he writes the result on is black, and doesn't look like a real piece of white card. He goes quiet with hand over mouth when the BBC announcer is doing the first announcing bit, after manically talking over the TV pictures up to then. The numbers are pointed upwards, and not at the camera directly and the balls are never moved into a more camera friendly position after the draw by Derren. The brick wall behind shot has a solid black line above the balls, and no other solid black lines anywhere on it of comparable size.
Could be highly trained fleas, I don't think ants would be quick enough to move into position in time - whereas fleas can just jump onto the balls from further away.
Guess 1: involves an accomplice hanging above the ball rack attaching numbers to each ball using some low tech means whos hidden behind a mirror/freeze thats lowered into place after the initial "camera2" establishing wideshot, then winched out of the way afterwards. which would mean that a studio audience would rumble it in no time - hence they are not there.
Guess 2: Variation of the split screen freeze camera trick (note that in a trailer you can view on DBs site that presumably aired on C4 tonight he is holding a snowflake, indicating freeze? as in frozen camera, or a "freeze" being lowered down to obscure an accomplice?, or just yet more misdirection) when he is quiet with hand on mouth the whole screen image is frozen he himself runs around to the other side to switch/mark the balls, hence the need for the black line and a dude talking into his ear that positioning is good for him to run back to his place and some slight camera wobble to disguise the fade back into live coverage, also meaning no live audience is possible.
meh, probably fleas
Or I could be completely wrong.