The 'Les Misérables' actress and the 33-year-old model - who broke up briefly in July - have reportedly called time on their relationship for the second time after their demanding careers have started to put a strain on their romance.
A source told the Daily Mirror newspaper: ''Both Samantha and David are in high demand professionally and are really busy with their careers. David's modelling is taking him all over the world and Samantha is the same - with regular gigs in America and Australia.
''With such packed schedules they were both finding it increasingly difficult to see each other.''
Just four months ago, David - who began dating Samantha in May - claimed he was single after he jetted off to New York for a job while the brunette beauty was pursuing her dreams in Los Angeles, but the pair appeared to patch things up almost immediately after they were spotted together at the Virgin Media V Festival in August.
David said previously: ''I am single at the moment.
''This summer I am going to Los Angeles and then New York. Samantha's gone to LA now and if I see her in LA then I see her in LA...
''I am not going to go out of my way to see her, but if I bump into her, I bump into her.''
The BBC drama starring Aidan Turner returns to BBC One on September 4th.
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