One group of housemates were sent into the luxury house, and the others were sent into a dilapidated basement.
After Dettori and Clark were introduced to the house, they were sent to the Diary Room where they watched videos of the entering housemates in pairs while they looked on outside with presenter Brian Dowling. Big Brother then asked them a "cruel" question which would determine which housemate went where.
First up were supermodel Paula Hamilton and Heartbeat star Tricia Penrose, and Clark and Dettori were asked who they thought would be more irritating. They chose to keep Penrose in the luxury house after Clark claimed that she seemed like "a right laugh".
Next up were Neighbours star Ryan Moloney and former EastEnders actress Gillian Taylforth. Big Brother asked who Clark and Dettori thought was the most fake. Declining to answer the question, the pair thought that Moloney would deal with the conditions in the basement better.
Corrie star Sam Robertson and glamour model Lacey Banghard were next in, and Big Brother asked the judging pair who they thought "loved themselves more". They chose Robertson, after Dettori claimed that he seemed "cocky".
Former Steps star Clare Richards and Neil 'Razor' Ruddock were next in, and Clark and Dettori were asked who they thought had the bigger ego. Both Ruddock and Dettori acknowledged some shared history, and Dettori sent him down after saying: "I met him in his heyday...he had a big ego then."
Finally, Heidi Montag and Spencer Pratt from MTV's The Hills were introduced, and Clark and Dettori were given the option of either sending them both down to the basement, or sending themselves down. The pair sent the reality show duo down to the basement with little hesitation.
Photo gallery - Celebrity Big Brother launch night: