Question: What English actor starred in the Stephen Poliakoff play Shout Across the River in London in 1978?

Context paragraphs:
Caught on a Train: Caught on a Train is a critically successful British television play written by Stephen Poliakoff and directed by Peter Duffell, based on an overnight train journey across Europe, and following the route of a journey that Poliakoff had himself made from London to Vienna.  It was first shown, on BBC1, on 31 October 1980, and was re-shown in 2001 and 2006.

City Sugar: City Sugar is a stage play by Stephen Poliakoff.  It was originally staged at the Bush Theatre in 1975 and directed by Hugh Thomas.  "City Sugar"’s cast was led by John Shrapnel as Leonard Brazil and supported by Leon Vitali and Lynne Miller.  In 1976 the play then transferred to the Comedy Theatre with Adam Faith taking over as Leonard Brazil and James Aubrey as Rex.  "City Sugar", along with its companion piece "Hitting Town", won Poliakoff the "Evening Standard"'s Most Promising Playwright Award in 1976.

Hitting Town: Hitting Town is a stage play written by Stephen Poliakoff and first performed in April 1975 at the Bush Theatre directed by Tim Fywell.  Written early in his career, the play won Poliakoff the "Evening Standard" Theatre Award for Most Promising Playwright.  The critic Michael Billington said it was "reminder of Poliakoff's precocious talent".

Daniel Jewel: Daniel Jewel is a London-based film producer and director.  A graduate of Bristol University and Oxford University he has worked with British film directors such as Stephen Poliakoff, Charles Sturridge and Brian Gilbert.  In 2006 he produced the play Allegiance at the Edinburgh Festival, which starred Michael Fassbender as the Irish leader, Michael Collins.  The play was directed by Brian Gilbert.  In 2007 he produced and directed two films for Channel 4 about the shisha smoking cafes of London's Arabic quarter.  In 2008 he directed two documentaries for Al Gore's Current TV.  In late 2008 his production company, Third Man Films produced Sidney Turtlebaum starring Derek Jacobi and Rupert Evans which The Times called a "Masterpiece" and was nominated for a British Independent Film Award and short-listed for an Academy Award in 2010.

Joe's Palace: Joe's Palace is a BBC television drama, (co-produced by the BBC and HBO) and written and directed by Stephen Poliakoff.  It was first aired on BBC One on 4 November 2007.  It is linked, by the central character of Joe, to the Poliakoff drama "Capturing Mary" which was aired (on BBC Two) on 12 November 2007.

Shout Across the River (1978): Shout Across the River is a stage play, written by Stephen Poliakoff, which premiered at the RSC Donmar Warehouse (at that time called The Warehouse) in London in September 1978.  It was directed by Bill Alexander.  It featured Gwyneth Strong in the lead role of a troubled eighteen-year-old girl.  The cast also included Lynn Farleigh, David Threlfall, Nigel Terry and Andrew Paul.

Richard Cunningham (actor): Richard Cunningham is an English actor known for playing Ryall in Stephen Poliakoff's Golden Globe winning "Dancing on the Edge", for the BBC with Chiwetel Ejiofor and Matthew Goode.

David Threlfall: David Threlfall (born 12 October 1953) is an English stage, film and television actor and director.  He played Frank Gallagher in Channel 4's series "Shameless".  He has also directed several episodes of the show.  In April 2014, he portrayed comedian Tommy Cooper in a television film entitled "".  In 2014, he starred alongside Jude Law in the thriller "Black Sea".

Capturing Mary: Capturing Mary is a BBC television drama (co-produced by HBO), written and directed by Stephen Poliakoff.  It was aired on BBC Two on 12 November 2007.  It is linked, by the central character of Joe, to another Poliakoff drama, "Joe's Palace", which was first aired on 4 November 2007.

Close My Eyes (film): Close My Eyes is a 1991 film written and directed by Stephen Poliakoff and starring Alan Rickman, Clive Owen and Saskia Reeves as well as Lesley Sharp and Karl Johnson.  Music was by Michael Gibbs (who would also provide the music for Poliakoff's next film, "Century") and the film was produced for Beambright and FilmFour International by Therese Pickard.

Supporting paragraphs: Shout Across the River (1978) David Threlfall
Answer: David Threlfall