Sarah Sands: Passion, drama, agony: a British institution in the making

On Friday evening, even as Scotland's latest most famous son saw his dreams dissolve at Wimbledon, the country's adopted daughter played out hers at Leicester Square.

Such passion, such drama, such agony. It could only be the pre- release screening of Harry Potter and the Half-Blood Prince. No wonder the Scots like to claim J K Rowling (on the basis she started to write when she moved to Edinburgh).

The cinema audience was asked to hand in mobile phones, presumably to prevent anyone from fashioning a miniature pirate video. Since this sixth book in the Harry Potter series has been read by most people in the world, selling nine million copies within the first 24 hours of publication, I can't imagine it was to prevent the plot line from coming out.

Four years ago, when we were on holiday in the Mediterranean, a friend coming through Gatwick on launch day kindly carried advance orders. She was mobbed as she arrived on Elba. No child had to be cajoled to read a book that summer. The only difficulty was persuading them to eat or sleep.

Recent interviews with the star actors in the film have mused on childhoods defined by Harry Potter. Warner Brothers is desperate to finish filming the final book before the cast start to have children themselves. Their fans, too, have grown up. Harry Potter and the Philosopher's Stone was published in 1997. I remember reading it to my three-year-old daughter.

On Friday she watched the film with me, a composed teenager of nearly 15. The audience was full of teenagers who were just the right age to sympathise with newly sexualised Harry, Ron and Hermione. Mischievous spells tend to do less damage in this film than fickle hearts.

The conspiracy theory among teenage Potter fans is that the film's release was delayed to allow some distance from its American rival Twilight. The books and films appeal to the same audience. Robert Pattinson, the starring vampire in Twilight, began his film career as Cedric Diggory in Harry Potter and the Goblet of Fire.

The latest Harry Potter is the most Twilight-like in its depiction of teenage romance. It is full of lunges and longing. Little Ginny Weasley is now dead cool and sexy. Because filming schedules have been racing to catch up with real-life puberty, there has long been a tension between reality and fantasy. Harry Potter's voice broke when he was still meant to be a child. Emma Watson as Hermione has bad hair and an emotional immaturity. Yet a couple of miles from the cinema are posters of the actress sleek and sultry, posing for Burberry.

Yet teenage snogging is not at the heart of Harry Potter, as it is with Twilight. It is not a rom com, it is a narrative epic – all the greatest stories ever told wrapped into one. The Twilight books are said to nod to Pride and Prejudice, Romeo and Juliet and Wuthering Heights. Harry Potter has everything thrown in from Dante to Beowulf to Dickens. Harry Potter and the Half-Blood Prince reminds me most of the Old Testament. Dumbledore as played by Michael Gambon is not the kindly old man we remember from Richard Harris's performance. He has turned into God.

How proud we should be of Harry Potter and the Half-Blood Prince as a glorious national institution. J K Rowling's great gift to British cinema was to insist on an all-British cast. The latest old darling to join is Jim Broadbent. Forget Wimbledon. We still rule the world with Harry Potter.

Sarah Sands is deputy editor of the London Evening Standard