Nicola Jane Walker[1] (born 15 May 1970) is an English actress, known for her starring roles in various British television programmes from the 1990s onwards, including that of Ruth Evershed in the spy drama Spooks (2003–2006 and 2009–2011), DCI Cassie Stuart in Unforgotten (2015–2021) and Hannah Stern in The Split (2018–2024).

Her voice roles include Doctor Who companion Liv Chenka in various Big Finish audio plays (2011–present) and Eleanor Peck in The Lovecraft Investigations (2019–2023).

[3] Offered a place at the Royal Academy of Dramatic Art on graduation from Cambridge, Walker already had some roles and an agent, so she decided to pursue her acting career.

[2] Walker's first major television roles were in 1997, as Gypsy Jones in Channel 4's adaptation of A Dance to the Music of Time, and as English teacher Suzy Travis in two series of Steven Moffat's school-based sitcom Chalk.

She played the leading part of DI Susan Taylor in the ITV thriller serial Touching Evil in 1997, co-starring opposite Robson Green.

Also in 1999, she took the lead role in the post-apocalyptic drama serial The Last Train, also screened on ITV (and written by future Spooks writer Matthew Graham).

Benji Wilson of The Daily Telegraph praised Walker's performance, stating: "an actress who has squeezed every drop out of TV’s greatest ever largely dumbstruck doormat for the best part of a decade.

[7] In 2007, Walker had a prominent supporting role as a child snatcher in the ITV1 drama serial Torn and appeared in the BBC adaptation of Oliver Twist.

From 2012 to 2020, she appeared as Gillian Greenwood (née Buttershaw) alongside Derek Jacobi, Anne Reid and Sarah Lancashire in five series of the BBC original drama Last Tango in Halifax.

[33] Walker won an Olivier Award in 2013 for Best Supporting Actress in her role as Judy, the main character Christopher's mother, in The Curious Incident of the Dog in the Night-Time.

[34] In 2014, she starred alongside Mark Strong and Phoebe Fox in Arthur Miller's play A View from the Bridge, at the Young Vic theatre.

In 2022 she starred as Miss Lily Moffat in the National Theatre revival in London of The Corn is Green, the 1938 autobiographical play by Emlyn Williams.

Her most prominent role was as one half of the folk duo in Four Weddings and a Funeral (1994), who sing "Can't Smile Without You" during the first church service and "Stand By Your Man" at the reception.

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.

Walker met actor Barnaby Kay when they worked together with the Out of Joint Theatre Company, in a 1994 touring production of The Man of Mode and The Libertine;[40] they married in 2006, and have a son, Harry, together.