Trev Costello, the brother of Carl Costello, arrived in the village as French interior designer "Alphonse", in November 2010 to help the Costello family redesign their kitchen and living room of their house. Carl's son, Seth, convinced Duncan Button that Trev fancied him.
Trev returned when Cheryl Brady hired him to redecorate Chez Chez. Cheryl's brother, Brendan, was homophobic towards Trev and tried to attack him when Trev suggested that Brendan was gay. Trev and Cheryl ended up sleeping with each other. The next day, Riley convinced Trev to tell Cheryl about himself. Cheryl was shocked when Trev tells her that his name wasn't "Alphonse", and that he had a wife and three kids. Cheryl continued to see him regardless, inviting him for a drink on New Year's Eve. They kissed, but Trev realised that he made a mistake and left the village, leaving Cheryl heartbroken.