First Night: Big Brother, Channel 4

"It's back," said Davina McCall, her tone hovering between threat and promise - and then that familiar yammering theme tune started up, gibbering hysteria in musical form. According to Davina, 100,000 people had thrown themselves at this juggernaut of factitious celebrity and, after false revelations in the tabloids and much ill-informed speculation, viewers were finally going to find out the lucky 12 who had managed to hit the windscreen. The basic rules were essentially the same, as were the chickens, the hot-tub and the lab-rat architecture - tweaked a little for the fourth series to press the contestants into greater intimacy.

But it was very quickly apparent that the chemistry was quite different this time round. With only four people in the house, the overall IQ already looked as if it had topped the last series' total and the next two confirmed that the producers had moved sharply up-market in their selection. The rent had definitely gone up. The contestants were better looking, more middle-class, and altogether calmer in their manner as they assembled. The opening hour on Series Three sounded like a seagull colony under attack from predators; this was more like the introductory drinks on a budget chalet holiday.

The contestants were all agreed on one thing - the essential insanity of the enterprise for which they just signed up. "This is mental," said Cameron, a Baptist from Orkney who had titilatingly confessed that he was in the market for a wife. "This is surreal," agreed Federico, a Scottish-Italian waiter. "This is mad. It's just crazy," volunteered Gos, an Indian head-chef who has an obvious advantage when it comes to securing the allegiance of his fellow inmates. Those who didn't question their own mental health called on a higher power for assistance, breath panting over the microphones which will be their constant companions for however long they stay inside the house. "Oh my God!" said Justine, Ray, Sissy and Steph. Tanya - the last inmate in and the most promising prospect for friction - just scrambled for her cigarettes.

Outside Davina - worth her weight in innuendos - was already winking and leering at sexual possibilities. The Everest of all reality game shows - the on-screen consummation - remains unconquered on British television and there are widespread reports that Big Brother's producers are anxious it should be scaled in this series. Bookmakers are already taking bets on when the flag will be planted and there are rumours that base-camp will be well supplied with alcohol - in an attempt to erase the unhelpful inhibitions which have defeated previous attempts.

What's more, where the last series bet big on wild discrepancies of character and appearance in the hope of generating nine weeks of watchable television, this one seems to have calculated that a broad similarity of age and attractiveness will be more productive.

"First impressions are going to be very important," Davina had promised towards the end of the first hour - scotching tabloid rumours that one contestant would be evicted last night, but hinting at a surprise in store for the new arrivals. They had to nominate their first choice for eviction before the night was out. Come back later, she ordered. And all over the country people who had said "I don't think I'll bother" or "It's not as interesting this time round" were murmuring: "Well - there's no harm in just seeing who goes first, is there? We don't have to get up early tomorrow."