Last year, a 16-year-old Italian girl, the niece of a friend, came to stay with me. It was her first time in London. What would you like to see, I asked — the tourist stuff, like Big Ben and the Tower of London? Or Carnaby Street, Selfridges and Hoxton? No, she said, I want to see the door. The door? The door from Notting Hill — the blue door where Hugh Grant lived. So we trotted over, asked around and found the door — except the blue door has been auctioned off and replaced by a new one painted a rich glossy black, so it looks like every second door in London. All the same, we took four photographs of her outside “the door” so she could show her friends when she got back to Arezzo.

It’s hard to think of another British film-maker who could inspire such Beatles-style devotion in a girl who was, after all, only seven years old when Notting Hill was released. The English Tourist Board hasn’t issued a guide to Guy Ritchie’s East End, after all. Richard Curtis, however, has delivered something of a low blow to poor Alessandra and her friends with his new film by setting it in the middle of the North Sea.

The Boat That Rocked is an unashamed tribute to the handful of pirate radio ships anchored off the UK coast during the 1960s, which broadcast rock’n’roll to a beat-starved nation rationed to two hours of pop a week by the BBC. At their peak, about 25m people — more than half the population of Britain — tuned into the pirates every day. Many of the DJs hailed from Australia or America, with their bustling, highly experienced pop music stations, and the on-air stars shattered the dreary RP intonation of bow-tied BBC announcers. Inevitably, the government decided that Something Must Be Done and, in 1967, outlawed any contact with the offending ships — which meant the stations’ advertising revenue was cut off and their supply ships were barred from sailing from UK ports, ultimately starving the pirates of revenue and even food. In a classic case of woolly government principle meeting nervous populist pragmatism, the BBC promptly hired most of the pirate DJs to front the launch of Radio 1.

The film boasts an astonishing cast: Oscar-winner Philip Seymour Hoffman as the loud Yankee main man on Radio Rock; Bill Nighy as the ship’s owner and captain, Quentin; Rhys Ifans as a cocky, sensual mike controller, Gavin; Nick Frost as the sarky jock Dave; and Kenneth Branagh as the cold, cruel minister determined to close down the fun. It’s the kind of cast in which Jack Davenport, Chris O’Dowd, Ralph Brown, Rhys Darby, Will Adamsdale, Tom Brooke and Mad Men’s January Jones “also appear”.

The film is less tightly focused than Four Weddings and Notting Hill — Curtis was inspired by National Lampoon’s Animal House and the M*A*S*H movie, which are closer to a series of loosely connected sketches than a narrative where each scene advances the next. And ultimately everyone, Hoffman included, plays second fiddle to the real star, Curtis’s lifelong passion: pop music. The film is drenched in the tunes of 1967, and the tomfoolery on Radio Rock is constantly cutting to scenes of hard-working Brits entranced by the pirate sound. There are even choreographed dance routines.

Curtis, 52, was born in New Zealand to a nomadic Unilever family, living in Sweden and the Philippines before settling at school in England, and pop was, ironically, his only constant in an ever-changing world.

“Pop music is absolutely my favourite thing,” he enthuses, sitting in a windowless room at the heart of BBC Television Centre during a brief muffin-and-coffee break from the chaos of preparing this year’s Comic Relief programming. “I’ve absolutely no talent at all, but so much enthusiasm. My dad had about eight records — Smetana, Mantovani, Nat King Cole, that sort of thing. But baby-sitters would come in with their box of records and put on the Supremes.

“When I lived in Sweden, I remember standing in the snow outside the Foresta hotel, waiting for the Beatles to come onto the balcony. And I have strong memories of being at school — where I was generally a well-behaved boy — but I’d sometimes hide in the music rehearsal rooms because Pick of the Pops exactly overlapped with chapel. I even remember standing against the radiator to get so hot that I could be put in the sanatorium by matron, so I could listen to the first playing of the Beatles’ White Album.” He stops and smiles. “I can even tell you that the No 1 this week is Flo Rida, with his cover of Dead or Alive’s You Spin Me Round. It’s always been my first love, so to make a movie about it was a logical thing.”

And clearly Richard Curtis movies are always about love. This is why impressionable adolescent Italian girls are drawn to him, and why cynical hacks and stand-up comics like to mock his work — albeit in such intimate detail, they’ve clearly watched everything from beginning to end. It’s unfashionable to love — if you send reams of fevered verse to the one whose mere existence can slice through your heart every minute of the day, you’re liable to get a restraining order. Curtis doesn’t even have the Byronic self-mutilation of a Romantic poet to justify his addiction to the emotion. He seems so damn nice: cheerful, softly spoken, self-deprecating and devoted to charity, founding Comic Relief and Make Poverty History, organising the Live 8 concerts.

So why has he returned to the lurching passion of alternating loss and fulfilment during two decades in which British cinema generally explored gangsters, identity and adversity in a series of grotty flats and suburban houses?

“It’s peculiar, isn’t it?” he muses. “I’ve never been very interested in unpleasant stories. I’m extremely interested in the unpleasant things in the world, which is why I spend half my time doing Comic Relief. For some reason or other, I’m more interested in writing about things I’ve enjoyed and that are meant to give people pleasure than I am in writing about murder. I can’t really explain it. I attribute it to a happy childhood with no residual anger.” He warns, however, that his embrace of on-screen joy may be about to end. “The other films I’ve been thinking of writing were one about my dad, who was very ill and died last year, and I’m halfway through writing a script about malaria.” He shrugs apologetically. “So I thought, you know, we deserved to have a bit of fun. The last-chance cafe before I become old and serious. ”

It’s tempting to search for Curtis in his movies. His 1989 debut, The Tall Guy, was set in Camden and featured Jeff Goldblum as Rowan Atkinson’s foil in a live West End show who courts a nurse — all technically true of Curtis at the time he wrote the thing. Four Weddings and a Funeral in 1994 charted Hugh Grant’s on-off romance with Andie MacDowell via meetings at various weddings. Curtis wooed Emma Freud, his partner and the mother of his four children, in similar circumstances. The pair even vowed never to marry, just as Grant and MacDowell swear eternal devotion to each other and their unmarried status at the film’s rain-soaked climax.

Explore Film

• Film Reviews

• Trailers

• DVD

• London Film Festival

Editor's choice

• The 100 Best Films of 2009
• The 100 Worst Movies of 2009
• The 100 Best Films of the Decade