The daughter of an Anglican vicar,[3] Walsh attended Christ's Hospital School, before going on to study History of Art at Gonville and Caius College, Cambridge, which she described as "the most boring three years of my life".

[4] While working in galleries, Walsh attended comedy writing evening classes including Stand up and Deliver and as a direct result wrote for Jo Caulfield on BBC Radio 4.

[8] She has appeared on TV shows, such as Edinburgh & Beyond on the Paramount Comedy Channel, The Late Edition, The Matt Lucas Awards, Mock the Week, QI,[9] and Would I Lie to You?.

[4][5] On 12 June 2009, Walsh was a guest panellist on 8 Out of 10 Cats, on 18 August 2009 appeared on You Have Been Watching, Newswipe with Charlie Brooker, and on 3 September on Mock the Week.

On 15 August 2010, Walsh sustained a suspected dislocated shoulder and fractured arm after leaping from the pier during the annual Worthing International Birdman festival.