The film is The Sea Change, a romantic drama about a marriage in crisis, “the thrills and difficulties of love”.
Scott Thomas is one of the industry’s most respected actors, with her career spanning roles in both English and French language productions.
Scott Thomas will star as Lillian, and Mark Strong, whose films include Tinker Tailor Soldier Spy, is in talks to play Emmanuel.
Kristin Scott Thomas is to make her debut as a director, three years after saying she had grown tired of film-making and would only pursue productions she could not resist.