Grant does a great Grant. Cary I mean. But the point applies equally well to the old eye-twinkler’s natural heir in the charm stakes – step forward please Mr Hugh John Mungo (I kid you not – kept that one a bit quiet Hugh-baby) Grant. Charm is an elusive quality much derided or mocked as in the old joke: English teacher to 12 year-old pupil – “now John, give me a sentence using the word charming.” “Well Miss, my 14 year-old sister told my Dad yesterday that she was pregnant and he said ‘charming, f****** charming.”

I digress. The two Grants are united in having one precious, natural gift – they have an irreducibly likeable screen persona. If Hugh’s grates a bit now and then while Cary’s carried him effortlessly through an almost flawless career, we may put it down to the older charmer having the advantage of working with some of the greatest comedy screenwriters in cinema. Hugh, as the sociologists say, has not had the same advantages. A bad script brings out the worst in our Mungo – he has to rely totally on his whole range of grimaces, shrugs and that funny little thing he does with his eyes that apparently makes women of all kinds, and I mean all kinds, want to hug him to bits. Or his bits.

Fortunately Marc Lawrence (II) (I’m going with ‘2’ not ‘11’ – but maybe I’m wrong) has come up with a script with a certain warmth and occasionally sharp enough to bring out the best of Hugh - his wonderful, if predictable, comic timing. So here the Grantian body-language of charm is put to the useful purpose of supporting a good script rather than carrying a bad one. Casting is good, with the always interesting, if not always winning, Drew Barrymore as Sophie Fisher, ditzy stand in plant-tenderer who even waters the plastic flowers. Barrymore offers a bit of feisty, klutzy spice to her seredipidous union with Grant’s Alex Fletcher - has-been pop idol reduced after a 20-year fame drought to reprising his 1987 bubblegum hit songs at county fairs etc where he is bottom of a bill headed up by John Deere (tractors). For light stuff like this, chemistry is all and you’ll buy into the credibility of these two cuddling up under Hugh’s Grand Piano. There is also nice little comic paradox about Hugh precious fastidiousness in never allowing anything, even a cashmere scarf, to sully the top of his prized piano, while a little sexual quavering underneath the said instrument is ok. Even if more upright than grand.

Having neglected to tell Alex that the Battle of the 80’s has-been’s TV show he signed him for required his client to out-box not out-sing his opponents, Alex's deservedly long-suffering agent comes up trumps with a chance to meet teen mega-star Cora (Hayley Bennett) a long-time Alex fan. Cora wants a new song – in 5 days. The only crimp in this seamless plan is Alex can write melodies, can’t write lyrics. Alex is working in his flat with drafted in lyricist Greg – long on misanthropy, short on intelligibility. Eavesdropping Sophie comes up with a few felicitous lines and rhymes that transform Greg’s drop-out’s manifesto lyrics into something can’t-get-the-bloody-thing-out-of-my-head catchy. Dump Greg – replace with Sophie. After some amusing and unconvincing “oh no I couldn’t” Alex and Sophie achieve a harmonious result, in bed and in music. Meanwhile off-the-wall Karmic krazy Cora likes the song and the happy ending set-up begins.

There is a thin backstory of Sophie’s failed affair with her English teacher who cad that he is, well he does teach English, made her the pathetic character in a successful novel. This pads out the plot enough to offer a few more engaging opportunities for Hugh to do his two-note schtick – here, nice nice guy William Thacker (Notting Hill) rather than nice nasty guy Daniel Cleaver (Bridget Jones). Cora’s mystic-chic Hindu-light feather brain has Sophie and Alex’s heartfelt little ditty turned into Madonna-esque weirdness which provokes some tosh between them about artistic truth and of course precipitates the pre-happy ending falling-out. At Cora’s big concert in Madison Square Garden, thinking Alex has nicked the credit for their song, a fleeing Sophie stops on her tearful way out to hear Alex express his love for her with his own first ever lyric performed like James Blunt on a mellow angst-free night. Cora and Alex then perform the Sophie/Alex penned song respecting the integrity of its true artistic form - somewhere between Freddy and The Dreamers and Gilbert O’Sullivan.

I mock, but this was all great fun. It had enough credibility and occasional wit to bounce along nicely keeping the smiles coming with a few unashamed ‘aaahhhs’ on the way to keep us helpless romantics feeling warm. The music is good enough to be credible with our Mungo (sorry Hugh, had to use it - just once more) displaying a pleasantly inoffensive light (in the loafers) breathy voice that holds a note without strain. The songs are tuneful and genuinely catchy in a kind of mirror image of Hugh’s acting: deceptively simple and seemingly easy to do – until you try it. As most British entries to the Eurovision song Contest discover each year. It really ain’t such a doddle.

Michael Apted tried to do a Hitchock (who cast Cary Grant against type in thrillers) with Hugh in Dangerous Measures. But like his namesake it didn’t really take – he’s really just too nice. And the better the scrip, the better he gets. He can wring every last shred of light comedy out of any line. And that is not a skill to sniff at. Drew Barrymore still awaits the sharp, sassy, fast-talking, intelligent part she was born to play and can really get her teeth into. But after a dodgy start she gives us a Sophie with a bit of edge.

A great date movie, and a good night out. For all but Grant-o-phobes.