Clive, who does not even appear in Act II, is primarily responsible for driving the action and the story of Act I. In a purely physical sense, Clive's frequent requests for others to enter or exit assures that the play is in constant motion and forces the characters to quickly adapt to changing circumstances.
In a thematic sense, all of the characters define themselves by their relationship to Clive. Betty is unable to act on any of her true desires because of her feeling of responsibility to Clive. Likewise, Edward subverts his homosexuality out of fear of Clive's reprimand. Clive is a symbol of the Act I's major theme: Oppression. He represents the colonial oppression of the British Empire in Africa, as well as the sexual oppression that defined social interactions in the Victorian Edward. Additionally, Clive represents the hypocrisy inherent to this oppression. He demands the loyalty of his family, while he himself is unfaithful to his marriage.
Although Clive holds the reigns of power for the majority of Act I, his status does depreciate. Despite his efforts to the contrary, his family spirals out of his control as members of his family begin to act on their sexual desires by the end of the act. In a final act of defiance, his own son fails to warn him of Joshua's murder attempt. Churchill does not bring Clive back in the second act of the play because, metaphorically, Clive is dead to the new world of Act II. His views are incompatible with the sexual liberation characteristic of London in 1979. Clive's absence in Act II might also suggest his family members' attempts to separate themselves from him.