Catherine Steadman is an English actress. She started her career in 2006, debuting on the ITV series The Bill. She next appeared on the TV movie Mansfield Park. Three years later, she made her film debut in Dust. This was followed by the film Princess Kaiulani. She also made appearances on the TV programs The Inbetweeners, The Tudors, Missing, and Law & Order: UK. In the 2010s, she played Ashley in the British film Salmon Fishing in the Yemen. She next appeared in the movie About Time. She went on to become known for her role as Mabel Lane Fox on Downton Abbey. She recently had guest roles on Tutankhamun, Midsomer Murders, and Victoria.