Name	Known for
Anthony Hopkins Gwyn Thomas Gwyn Thomas See fewer	The Silence of the Lambs (1991)
Sue Roderick Lyn Thomas Lyn Thomas See fewer	Under Milk Wood (2015)
Robert Pugh Gwyn's father Gwyn's father See fewer	The Ghost Writer (2010)
Brendan O'Hea Gwyn (aged 18) Gwyn (aged 18) See fewer	Quantum of Solace (2008)
Gavin Ashcroft Gwyn (aged 13) (as Gavin Rhys Ashcroft) Gwyn (aged 13) (as Gavin Rhys Ashcroft) See fewer	Y Mapiwr (1995)
Bernard Lloyd Walt Thomas Sr. Walt Thomas Sr. See fewer	The Young Victoria (2009)
Richard Lynch Walt Thomas Jr. Walt Thomas Jr. See fewer	The Hollow Crown (2012)
Abigail Hopkins Nana Thomas (as Abigail Harrison) Nana Thomas (as Abigail Harrison) See fewer	Under This Sky (2024)
John Grillo Dr. Bronowski Dr. Bronowski See fewer	Brazil (1985)
John Edmunds Chairman of Brains Trust Chairman of Brains Trust See fewer	Lifeforce (1985)
Alan David Headmaster Headmaster See fewer	The Painted Veil (2006)
Ann Beach Headmaster's wife Headmaster's wife See fewer	Notting Hill (1999)
Sion Probert Mr. Metcalfe Mr. Metcalfe See fewer	Grand Slam (1978)
Victoria Plucknett Mrs. Metcalfe Mrs. Metcalfe See fewer	The Duchess of Duke Street (1976)
Robert Hands Baker Baker See fewer	Anna and the King (1999)
James Arlon Clarke Clarke See fewer	Castles (1995)
Benjamin Whitrow Principal Principal See fewer	Chicken Run (2000)
Rowena Cooper Mrs. Morris Mrs. Morris See fewer	Poirot (1989)
Geoffrey Hutchings Walford Walford See fewer	Topsy-Turvy (1999)
Ian McDiarmid George Devine George Devine See fewer	Star Wars: Episode III - Revenge of the Sith (2005)