Alex inherits Oakwell Hall at a young age and becomes engaged to family friend, Tara Cockburn. He meets Kim Tate and is attracted to her. Kim pursues Alex and invests in his stud farm business. They have an affair and Alex shows a lot of interest in Kim, even after he marries Tara. Alex develops a substance abuse problem. During a party at Home Farm, Kim catches him taking cocaine. Alex flirts and dances with Linda Fowler and he offers to drive her home. Due to the cocaine and alcohol he had consumed, Alex crashes the car into a tree. Seeing Linda is unconscious, Alex moves her to the driver's seat and kisses her goodbye. He then flees the area. Alex returns the following year and holds Steve Marchant, Biff Fowler and Ned Glover hostage. In a plan to destroy Alex, Tara agrees to leave with him but he steals her jewellery and leaves without her.
Linda's younger brother, Roy, later learns Alex has resurfaced in London and is using the name Sinclair in the London Metropolis Hotel. Roy goes after Alex, unaware that Alex's associate, Dan Campbell, is actually an undercover officer who is attempting to get sufficent evidence to get Alex and his other associates sent to prison. However, after Dan holds Kathy Glover, Marlon Dingle, Eric Pollard and Roy captive in the office of a warehouse and refuses to shoot them on Alex's orders, Alex learns that he is an undercover officer. Roy becomes outraged when Dan offers to let Alex go, telling him that he's after Alex's associates, and attacks Alex. Alex attempts to shoot Roy but accidentally shoots Dan instead, and runs off with Roy in pursuit. They have a brutal fight and Roy ends up knocking Alex's gun out of his pocket whilst trying to pull Alex from the ladder leading to the roof. Roy picks up the gun and threatens to shoot Alex. Alex pleads for his life, offering Roy all of the money from the jewels he has, but Roy refuses. Alex ends up falling from the roof, grabbing onto a ledge. He pleads for Roy's help, but Roy watches as Alex loses his grip and falls to his death. Dan helps Roy make Alex's death look like an accident.