The new, uncomplicated Meryl Streep stars again

Middle age used to spell the end of a film career, particularly for actresses. But Meryl Streep, who stars with Alec Baldwin in the new 'September to September' romantic comedy, It's Complicated, is proof that advancing age is no longer an automatic career impediment in Hollywood.

In Nancy Meyers's film, which opens in Britain on Friday, Streep and Baldwin play divorced Santa Barbara couple Jane and Jake Adler who split up when he dumps her for a much younger woman (Lake Bell). A decade later, Streep is only coming to terms with her divorce when the graduation of their youngest child throws the pair together at a party in New York.

A chance meeting at the bar culminates in a night of drunken passion (most of which takes place under the covers). Back in Santa Barbara, the boozy fling becomes a giddy affair, as Jake and Jane meet up behind both their partners' and children's backs.

Meyers, who also celebrated middle-age sexuality with her 2003 film Something's Gotta Give starring Diane Keaton and Jack Nicholson, has received mixed reviews for It's Complicated. But this hasn't put off the film's main demographic, women over 40, for whom Streep is an undeniable attraction. So far, It's Complicated has grossed more than $60 million in the United States.

The film also sees Alec Baldwin excel in his first big-screen feature since Tina Fey cast him in 30 Rock, the TV sitcom which has transformed his career. The former Hollywood pretty boy and ex-Mr Kim Basinger is not just funny but is willing to literally draw belly laughs as he flaunts his middle-age spread for comic effect.

For Streep, It's Complicated is the latest in a string of films that has seen her become the actress of choice for her generation, proving that you can still do sexy, strong and comic roles at 60. Not only that, but she is nine years older than her on-screen husband Baldwin, 51, which is something of a Hollywood casting milestone.

Since 2006, when she played the withering, Anna Wintour-esque fashion editor in The Devil Wears Prada, Streep has been on a late-in-life career roll – her hottest run of films since the 1980s when she won Oscars for Kramer vs Kramer and Sophie's Choice.

And the new films are a world away from these earlier, more serious works. In recent roles, such as the lead singer of a girl group in Mamma Mia! (2008), Streep looks relaxed and sensual. In last year's  Julie & Julia, she stole the show as the venerable chef Julia Child.

Where Streep once came across in interviews as almost pompous, consumed by her method acting and mastery of those many accents, she now seems happy to be seen enjoying herself, frequently laughing with journalists – and very much at ease in her new role as Hollywood's leading mature-but-sexy screen siren.

WHAT THE CRITICS ARE SAYING:

Kirk Honeycutt, the Hollywood Reporter: "Streep is a vision of mature loveliness, a smart, sexy mom who always knows the right things to say to the kids and how to extricate herself from embarrassing situations. Unlike the real world, she lives in a multiple-million-dollar home, can - after a suitable number of comic mishaps - make sense of her life and even get Skype to work without having to consult younger family members."

Manohla Dargis, the New York Times: "Much as Diane Keaton did in Something's Gotta Give, Ms Streep, mugging wildly if winningly, takes this character and makes you love her, just as Mr Baldwin does with Jake, who, with his shark smiles and thrusting gut, beautifully conveys male vanity in its twilight."

Anna Smith, Time Out: "Baldwin has terrific chemistry with Streep: the pair seem to be having a genuinely hilarious time getting drunk and naked together – not that Jane will do that with the lights on. The script explores female insecurities and doesn't shy away from the realities of middle-aged sex… Streep is as enjoyable as ever, and if laughs count for anything, this is one of the better romantic comedies of the season." (Verdict: three stars out of five)

Betsy Sharkey, the Los Angeles Times: "Meyers has been working through her issues on screen for at least 20 years, starting with Baby Boom in 1987 through Something's Gotta Give in 2003. But the vulnerability and smartness as well as the funny, with which she infused those earlier films, are harder to find here." ·