[citation needed] Harker has acted in both contemporary and classic works, on stage, in movies and in TV series.
In 1990–91 she appeared alongside Clive Owen in Chancer, and as the journalist Mattie Storin in the original House of Cards.
She is featured as Emma Fitzgerald, the love interest of Superintendent Tyburn (Trevor Eve) in the BBC TV series, Heat of the Sun (1998).
In 2003 she played Clare Keightley in the audio version of the Doctor Who adventure Shada, alongside Paul McGann.
On stage in 2005, she appeared in Simon Stephens's play On the Shore of the Wide World at the Royal National Theatre.