Derren Brown: Trick Or Treat (C4, 10pm); Sexcetera (Virgin 1, 11pm)

WHAT exactly is Derren Brown?

Is he a magician, a psychological trickster or just someone who meddles with your mind?

A bit of all three judging by the first in his new Trick Or Treat series. There's no illusion as such, but plenty of mind games.

The premise is that a volunteer, who's answered a newspaper appeal for participants, must pick a card from two offered by Brown. This blind choice offers either a pleasant experience - the treat - or a darker trick.

Glen, a 40-year-old father of two from Essex who works as an aviation insurance specialist, strikes lucky. He wins a treat. Of course, the showman in Brown won't allow Glen simply to enter a room and pick a card. He has to be ambushed in a lift where he's observed by a hidden camera and taken to a room for the card selection. It's a silly piece of theatre to liven up the programme because Glen's task is to read books for seven days.

He's taken to Kings College Library in London where the shelves are filled with almost one million books containing the general knowledge of the world. Glen is surprised to learn that Brown is going to show him how to absorb all those facts and figures so he can compete in the pub quiz of pub quizzes, The Night of the Champions.

As Glen reckons he doesn't have a good memory, this seems like a mission impossible.

Not so, insists Brown, as he makes Glen remember something that happened on his way to work that he was, until prompted, unaware he'd seen.

"That's the most bizarre episode in my life,"

he says. But he ain't seen nothing yet. "I must expand his memory capability so he can absorb huge amounts of information," Brown explains.

This involves speed learning, which amounts to looking at a page in a book and storing it in your head. Apparently the knowledge fades away after a few days if not used.

All this sounds ridiculous. Surely Brown can't possibly turn Glen into a memory man able to compete against the cream of pub quizzers? Oh yes, he can.

He gives us an example of this extension of photographic memory by getting a coffee shop barista to spill the beans - on a tray. He's asked to select a single bean, mark it with an X and replace it. Brown, having previously lodged images of the bean patterns in his brain, is able to pick out the X-factor bean from the 1,347 on the tray.

Before the pub quiz, Glen is tested by being given a few questions to answer by Brown, plucking information at random from the books his pupil has been reading.

Glen is able to dredge up the fact that 319 different sorts of humming bird have been recorded in the Amazon rainforest. He didn't know he knew that. It just emerges from somewhere in the depths of his brain and into his mouth when Brown asks the question.

How does that feel? wonders Brown.

"Scary," replies an understandably bemused Glen.

JUST as frightening are some of the sights you come across flicking through Freeview channels late at night. Like Sexcetera, which seems to be on Virgin 1 most nights.

As you might gather from the title, this is about sex, but what makes it different is that reporters feel obliged to join in. So presenter Valerie happily strips off during an item on finger painting to have her naked body daubed with paint (and not just her finger).

Reporter Donna is shown riding a pony girl - a topless woman on all fours, wearing a bridle and saddle - as she assures us that most couples indulging in equine games are in long-term relationships and not just horsing around.

Likely lads Frank and Hoyt visit an internet adult radio station whose programme presenter is called Wankus and whose workers are mostly porn stars.

This is the 21st Century version of pirate radio. Thanks to the internet you can see what you're listening to. You see rather more than you do on the webcam in the BBC Radio 5 studio.