During 1985 Jan is mentioned numerous times by Angie Watts as she knows her husband Den Watts is having an affair with her and goes on holiday with her. Den Watts had an affair with Jan for years, something which his wife, Angie Watts was aware of.
Jan appears in 1986 as the long-term mistress of Den Watts. Jan is a posh upper-class sort of woman and works at an art gallery. Den has an affair with her while he is still married to Angie Watts. She is always hated by Angie and Den's adopted daughter Sharon Watts but she tries her best to get along with her. She moves into The Queen Victoria at one point on Den's insistence, but isn't much of a landlady so moves out soon after. Den tries to leave Angie for Jan so he tells Angie he is leaving her. Angie grows desperate and in order to stop him from leaving her she lies to him by saying she has six months to live. Den believes her but discovers many months later that she is lying while they were on holiday in Venice.
In one of EastEnders most famous storylines, he serves her divorce papers on Christmas Day 1986. Eventually Jan grows tired of Den not having a proper relationship with her so she ends their affair after he refuses to leave Walford with her. She leaves Walford in 1987 and then went on to marry a man called Dario Chimisso on a gondola in Venice. She makes a brief return in 2002 for Angie's funeral. She returns to give Sharon a portrait that Den had left with her many years earlier.
She briefly returns again in 2003 in a lead-up to Den's return 14 years since he has been shot and presumed dead by an employee of the gangland organisation The Firm. Den's long lost son Dennis Rickman tracks Jan down and she reveals that Den had survived the shooting and came to her for help. With her help, Den was able to flee to Spain to protect himself and his family.