In July 2011, Walker played the significant supporting role of Medtech Liv Chenka in the Big Finish Productions Doctor Who audio drama Robophobia, opposite Sylvester McCoy as the Seventh Doctor. The Chenka character proved popular both with producers and listeners, and in February 2014 Walker returned to the role, this time as a foil for Paul McGann's Eighth Doctor in Dark Eyes 2. The character was sustained throughout Dark Eyes 3 and Dark Eyes 4, at the end of which it was revealed that Chenka was to continue as the Doctor's established travelling companion. In October 2015, Walker again returned to the role in the first volume of the 4-volume Doom Coalition. In 2017, she starred in the company's adaptation of the H.G. Wells novel The Shape of Things to Come.