He's a confirmed bachelor (and convicted kerb-crawler) in his mid-40s; her two marriages lasted a total of 14 months. In the real world, Hugh Grant and Drew Barrymore would be the last people you’d turn to for lessons in romance.

Yet even their flimsiest flights of fancy usually end up atop the movie charts, buoyed by the stars' natural, self-effacing personalities. Music And Lyrics is thus destined to be a hit.

Amounting to no more than an extended, improvised comedy sketch, it opens amusingly enough with a 1984 video from Pop, an 80s boy band whose dance moves are even dodgier than their hairdos.

Two decades later, Pop’s Alex Fletcher (Grant) is still on vocals and keyboards. Only now he’s out on his own, playing school reunion gigs to the delight of his ageing female fans.

Alex also has a fan in Britney-meets-Barbie pop sensation Cora (newcomer Haley Bennett, who has no hidden talents). She wants Alex to write her a new song. The problem is, lyrics are not his forte.

With a deadline of mere days, Alex benefits from the miracle of the rom-contrivance: his stand-in plant-waterer Sophie (Barrymore) has a way with rhyming couplets. Together, they make sweet music.

But the happily-ever-afters must wait until Sophie deals with her past (involving Campbell Scott as the smartypants ex who turned their relationship into a tawdry bestseller) and Alex does something about Cora ruining their beautiful song.

He says she actually likes to play the victim so she can hide from reality. Wham! She says he has no artistic integrity and is scared to write anything that comes from the heart. Take that.

The redoubtable Kristen Johnston (formerly of ER) provides entertaining back-up as Sophie's big sister, but neither Scott nor Everybody Loves Raymond's Garrett (as Alex's manager) are given much to do.

A single striving to be an LP, Music And Lyrics is just about carried off by Hugh's blinky charm, Drew's good-girl kookyiness and a sprinkling of cute pop culture gags (most of which will bypass the under 20s).

It would make a perfect triple bill with Two Weeks Notice - director Lawrence's last collaboration with Grant - and Barrymore's Never Been Kissed.

After all, things this throwaway always come in threes.

Elliott Noble