| Year | Title | Role | Notes |
| 1993 | The Bill | Mrs. Heaton | Series 9; Episode 154: "Cause for Concern" |
| 1997 | Ruth Bell | Series 13; Episode 43: "A Bitter Pill" |
| 1998 | The Gift | Jo | Television film |
| 2001 | Judge John Deed | Natalie Abbott | Series 1; Episode 1: "Rough Justice" |
| 2002 | Dalziel and Pascoe | Megan Lowry | Series 7; Episode 1: "The Unwanted" |
| Tipping the Velvet | Alice Astley | Mini-series; Episode 1 |
| 2005 | Wallis & Edward | Elizabeth | Television film |
| 2006 | Agatha Christie's Poirot | Cora Gallaccio / Miss Gilchrist | Series 10; Episode 3: "After the Funeral" |
| The Commander: Blacklight | DC Pamela Hayes | Television film |
| 2007 | The History of Mr. Polly | Annie Larkins | Television film |
| 2008 | Great Performances | Regan | Series 37; Episode 12: "King Lear" |
| 2009 | Occupation | Nicky Swift | Mini-series; Episodes 1–3 |
| U Be Dead | Maria Marchese | Television film |
| Midsomer Murders | Imogen Stroud | Series 12; Episode 7: "The Great and the Good" |
| 2010 | Excluded | Amanda | Television film |
| DCI Banks: Aftermath | Maggie Forrest | Series 1; Episodes 1 & 2: "Aftermath: Parts 1 & 2" |
| 2011 | Appropriate Adult | Rosemary West | Mini-series; Episodes 1 & 2BAFTA TV Award for Best Supporting Actress |
| 2012 | Coming Up | Lisa | Series 10; Episode 4: "Spoof or Die" |
| 2013 | Call the Midwife | Meg / Mave Carter | Series 2; Episode 3 |
| Complicit | Judith | Television film |
| The Escape Artist | Eileen Morris | Mini-series; Episodes 2 & 3: "Parts 2 & 3" |
| 2014–2024 | W1A | Tracey Pritchard | Series 1–4; 16 episodes |
| 2015 | Wolf Hall | Alice More | Mini-series; Series 1; Episodes 2 & 4: "Entirely Beloved" and "The Devil's Spit" |
| The Casual Vacancy | Tessa Wall | Mini-series; Episodes 1–3 |
| 2016 | Mid Morning Matters with Alan Partridge | Angela | Series 2; Episodes 1 & 4: "Foxhunter + Radio Play" and "Jasper + Chef" |
| Neil Gaiman's Likely Stories | Dr. Marshall / Café Manager / Nora / Miranda Walker | Mini-series; Episodes 1–4 |
| The Witness for the Prosecution | Janet McIntyre | Mini-series; Episodes 1 & 2 |
| 2017 | Death in Paradise | Patricia Lawrence | Series 6; Episode 2: "The Secret of the Flame Tree" |
| Catastrophe | Polly | Series 3; Episode 2 |
| Strike | Leonora Quine | Series 1; Episodes 4 & 5: "The Silkworm: Parts 1 & 2" |
| 2018 | Inside No. 9 | May | Series 4; Episode 3: "Once Removed" |
| A Very English Scandal | Marion Thorpe | Mini-series; Episodes 2 & 3Nominated — BAFTA TV Award for Best Supporting Actress |
| Vanity Fair | Mrs. Peggy O'Dowd | Mini-series; Episodes 4–7 |
| Hang Ups | Alison Jones | Episodes 1 & 3 |
| God's Own County | Jackie | Television short film |
| 2019 | Christmas University Challenge | Herself - Contestant | Series 9; Episode 3: "Guildhall School of Music and Drama v UCL" |
| Urban Myths | Catherine Dickens | Mini-series; Series 3; Episode 1: "Bleak House Guest" |
| 2019, 2023 | Black Mirror | CS Linda Grace,Janet McCardle | Series 5; Episode: "Smithereens",Series 6; Episode 2: "Loch Henry" |
| 2020 | Unprecedented | Kat | Episode 4 |
| Talking Heads | Lorna | Episode 12: "The Shrine" |
| 2022 | The Thief, His Wife and the Canoe | Anne Darwin | Mini-series; Episodes 1–4 |
| My Name is Leon | Maureen | Television film |
| 2023 | The Change | Carmel | Series 1; Episodes 1–6 |
| 2024 | Celebrity Chase | Herself - Contestant | Series 14; Episode 2 |
| Mr Bates vs The Post Office | Jo Hamilton | Mini-series; Episodes 1–4 |
| Comic Relief: Funny for Money | Tracey Pritchard | Television film |
| Inside No. 9 | May | Series 9; Episode 6: "Plodding On" |
| Sherwood | Ann Branson | Series 2; Episodes 1–6 |
| A Ghost Story for Christmas | Mrs. Dorman | Episode 18: "Woman of Stone" |