July 2000: The first series of Big Brother launches with Southern Comfort as its sponsor. The show, featuring the likes of Nasty Nick, brings Channel 4 its highest audience share ever. The final show peaks with ten million viewers, a 56.5 per cent audience share.
2001: After the success of the first series, BT Cellnet spends an estimated £4 million to sponsor Big Brother's return. Big Brother 2 builds on the success of the first series, but its final show, featuring a vote between Brian Dowling and Helen Adams, attracts fewer viewers, with a peak audience of eight million.
2002: O2, the company born out of BT Cellnet, commits to backing the third series of the show. The mobile operator's commitment is rewarded after an unprecedented ten million text votes are received from viewers. Kate Lawler scoops the £70,000 prize and the third series beats the previous two in terms of viewing figures.
2004: After a lacklustre Big Brother 4 the previous year, 02 pulls out. Its chief executive, Peter Erskine, describes the show as "a bit old-hat" and is none too keen on some of the hanky-panky going on. But this doesn't stop Carphone Warehouse's TalkTalk brand taking its place. Big Brother is won by the transsexual Nadia and some of the old excitement returns with a series of fights in the house.
2005: TalkTalk returns to sponsor Big Brother 6, which attracts 7.8 million viewers, a 34.4 per cent audience share, for the final show. This is down on previous peaks but is still Channel 4's most-watched show of the year. Geordie dancer Anthony Hutton triumphs.
2010: Big Brother morphs into an internet and mobile-only event, with viewers able to contact members of the house to ask them to perform songs and intimate acts for a one-off text charge of £50. Crazy Frog takes over as the sponsor of the show on the condition that contestants sing one of its ringtones every minute.