The attention-drawing piece of casting at the centre of the mini-series is that of David Tennant, best known as the tenth incarnation of Doctor Who (1963-89, 2005– ), as the disturbed ex-boyfriend. Moreover, Tennant plays the part employing the same cockily nonchalant cheer that he does as The Doctor, but twisting it towards a decidedly sinister undertow. At one point during the party held to announce his engagement to Claire Goose, he approaches Kate Ashfield while the others are away and smilingly tells her: “I was just looking at your mouth ... and thinking I’d come into that mouth.” Perhaps the one thing we do not gain is any insight into is how Tennant manages to wield such hyper-charm on so many people throughout – all of whom seem to have switched off their safety regulations about strangers. There are also fine performances from both Kate Ashfield and Claire Goose as the two sisters.

Secret Smile is directed by veteran British director Christopher Menaul, who was also responsible for works such as Prime Suspect (1991), Fatherland (1994), The Passion of Ayn Rand (1999) and See No Evil: The Moors Murders (2006). We get a fine sense of Kate Ashfield continually biting down on what she thinks for the sake of sister Claire Goose as no-one else around her can see or is even willing to countenance the things that she knows about David Tennant. Especially good is a family dinner scene where she wheels out all the evidence she has gathered against Tennant and he effectively manages to turn it around or minimise it to make it seem that the real problem is her resentment. The story more than effectively draws us in inside Kate Ashfield’s obsession to frequent points where it can pull back and make us realise that, even though she might be right in what she believes, she has become unbalanced in her single-minded obsession.

It is this that leaves one balking at the final solution to the problem that Kate Ashfield pulls off. [PLOT SPOILERS]. One where she, along with the help of David Tennant’s current woman (Keira Malik), conspire to make police think that Tennant has murdered her. Here the film has us swallow the fact that it is acceptable for the heroine to conduct a major fraud and frame a man to go to jail for life. Her only real reason for perpetrating this is that she merely believes he may have murdered her best friend (something that police can find no evidence of) and pushed her brother to stop taking his meds, which made him suicidal, all over a relationship that lasted for 10 days. While Kate Ashfield is an entirely sympathetic character throughout, when the steadiness of the evidence is looked at in a more rational light, you cannot help but wonder who the unbalanced one was.