She played Princess Diana in a TV film, Whatever Love Means, opposite Olivia Poulet as Camilla Parker Bowles and Laurence Fox as Prince Charles.

[9] Duncan lent her voice to an adaptation of The Little Mermaid[10] by Hans Christian Andersen at Little Angel Puppet Theatre in 2006 alongside Dame Judi Dench, Sir Michael Gambon, Rory Kinnear, Claudie Blakley, Rosamund Pike, Claire Rushbrook and Peter Wight.

[18] She took the role of Bea[19] (originally performed by Helen Baxendale) in Deborah Bruce's play The Distance, directed by Charlotte Gwinner, for Sheffield and the Orange Tree Theatres.

In the same year, Duncan starred opposite Dougray Scott in the short film Slay and Prepare the Animal for Meat, directed by Oisin Kearney and written by Ciara Elizabeth Smyth.

In 2023, Viaplay announced that Duncan had been cast in the Rebus reboot series based on the crime novels of author Ian Rankin.