The residents of the fictional village of Greendale are sitting on the secret to eternal youth.

Trusty postman Pat Clifton has been doing the rounds with his black and white cat Jess since September 1991 and during those 23 years, he doesn't appear to have aged a day.

Alas, screenwriters Kim Fuller, Annika Bluhm and Nicole Dubuc don't appear to have taken a refreshing swig from Greendale's rejuvenating water supply before they penned the lifeless and shambolic script to Pat's computer-animated big screen debut.

Postman Pat: The Movie is a shadow of the beloved stop-motion TV series, exploring the poisonous effects of celebrity on the mild-mannered postie when he becomes involved in a televised singing contest.

If the premature closure of West End show I Can't Sing - The X Factor Musical proved anything, it's that these talent searches are already garish pantomimes that defy parody.

Fuller, Bluhm and Dubuc disagree and clumsily satirise the format, casually throwing in romance and a hare-brained sci-fi invasion plot to the unappetising mix.

Postman Pat (voiced by Stephen Mangan) is at the heart of village life in the cosy community of Greendale, where he lives in Forge Cottage with his wife Sara (Susan Duerden) and football-mad son Julian (Sandra Teles).

Sara has always dreamt of going to Italy, so when Pat discovers a trip for two is the top prize in the TV reality show You're The One hosted by Simon Cowbell (Robin Atkin Downes), he prepares to belt out a ballad.

"Think of it as singing in the shower," Julian tells his father soothingly, "but in front of lots of people... and with your clothes on."

Against the odds, Pat's audition charms the usually stony-faced Cowbell.

Within days, Pat has become a nationwide celebrity and he gets caught up in the media hoopla, which takes him far away from his loved ones and his job at the Special Delivery Service (SDS).

In Pat's absence, SDS efficiency expert Edwin Carbunkle (Peter Woodward) plots to replace all of the human staff with robot doppelgangers.

Meanwhile, the grand final of You're The One beckons and Pat prepares to compete against teenage singer Josh (Rupert Grint) and his pushy father (David Tennant).

Postman Pat: The Movie is a second-class delivery of a hackneyed plot.

Oddly, the film opens with Cowbell auditioning a blond Irish singer called Ronan, who is voiced by Keating, sings one of his hits and cheekily claims to have some experience "in the business".

Cowbell dismisses this wannabe and within 20 minutes, we discover Pat also has the same distinctive Dublin-twanged singing voice. Bizarre.

Animation throughout is competent and the handful of gags pitched at snoozing adults, like the screen display of a robotic Jess which reads Faster Pussybot Kill Kill, barely warrant a weary smile.

Pat by name, pat by nature.