Movies:
* The Queen (2006): As Tony Blair, the Prime Minister of the United Kingdom during the aftermath of Princess Diana's death. This role earned him a BAFTA Award nomination for Best Supporting Actor.
* The Constant Gardener (2005): As the corrupt British diplomat, Jasper Rose.
* Enduring Love (2004): As Joe Rose, a man obsessed with a journalist.
* The Debt (2010): As Stefan, a former Nazi war criminal.
* Tamara Drewe (2010): As Nicholas Hardiment, a novelist struggling to write.
* The Lady in the Van (2015): As Alan Bennett, the playwright who lived with an eccentric woman in his driveway.
* Judy (2019): As Bernard Delfont, a British theatrical impresario.
* The King's Man (2021): As "The Shepherd" - a mysterious figure who trains a young Kingsman agent.
* The Batman (2022): As the voice of Oz, a corrupt and ambitious Gotham City police captain.
Television:
* Endeavour (2012-2022): As DI Fred Thursday, a detective inspector in the Oxford City Police. The series is a prequel to the classic Inspector Morse detective series.
* The Thick of It (2005-2012): As Peter Mannion, the Minister for Social Affairs. This role earned him a BAFTA Award nomination for Best Supporting Actor.
* Rev (2010-2014): As Adam Smallbone, an overworked and stressed Anglican vicar.
* Game of Thrones (2016): As Qyburn, a master of whispers and a key figure in the power struggles within King's Landing.
* The Good Lord Bird (2020): As John Brown, a close friend and confidante of John Brown.
* The Sister (2020): As Bob, a man concealing a dark secret.
* The Capture (2019-2022): As DI Rachel Carey, a detective investigating a potential miscarriage of justice.
* The Crown (2022): As Lord Mountbatten, a senior figure in the British Royal Family.
This list is not exhaustive but highlights some of Allam's most notable roles. He continues to be a sought-after actor, known for his versatility and strong performances.