<Li> Clare - Hope Ashitey as Carly Williams, a patient of Gemma's, who helps support Gemma, due to her suspicions of Simon . </Li> <Li> Cheryl Campbell as Helen Foster (episodes 1 - 3) </Li> <Li> Jodie Comer as Kate Parks, a 23 - year - old University graduate who has been secretly having a two - year affair with Simon Foster . </Li> <Li> Navin Chowdhry as Anwar (episodes 2 - 3, 5) </Li>

Who is doctor foster's husband having an affair with