Let's get one thing straight here: I adore Melissa McCarthy and think she's one of the great comic actors of her generation. But what we have here is her trying to carry a film almost on her lonesome, as she plays the central character, co-wrote the script (with director and husband, Ben Falcone), and is almost omnipresent for the duration. It doesn't really work and the problem is a script that's more flimsy than funny.

The plot's straightforward. Tammy (McCarthy) loses her crummy burger joint job after arriving late due to her accidentally crashing her car into a deer. Arriving home early, she discovers her husband Greg (Nat Faxon) enjoying a meal with neighbour Missi (Toni Collette).

Deflated by the loss of her job and to discover her husband's been cheating on her, Tammy decides to leave town and heads for the house of her mother (Alison Janney), who refuses to give her the car when she demands it.

Up steps Tammy's grandmother (Susan Sarandon), a hard-drinking, foul-mouthed individual who convinces Tammy to take her car, with her in it, when she offers up a hefty roll of banknotes for her passage.

The road movie that follows isn't quite Thelma and Louise - a movie that couldn't be ignored here given Sarandon's pivotal role in the 1991 classic road movie directed by Ridley Scott – but it does have its endearing moments. What this film seriously lacks, however, is some funny lines.

A couple of adventures create a strong bond between Tammy and her granny, while Kathy Bates lends her magnetic presence to the film when she appears mid-way through the story. But what we have here is Melissa McCarthy and her real-life hubby learning the ropes in terms of comedy-writing.

One day, hopefully someday soon, Melissa McCarthy will be able to pen a script that her wonderful acting ability deserves. Unfortunately, Tammy isn't it.

John Byrne