1846 GMT: And as the stars head to Leicester Square for the screening, that's it from us. Thanks for reading.
1845 GMT: Stars, director, producers and Rowling now posing on the stairs for group photos.
1844 GMT: The story will always live on for fans, says Rowling. "Hogwarts will always have a place for you," she says. After many more tearful thanks, she announces that they're going to roll the film.
1841 GMT: "Maybe I'll just write another one," Rowling says, wiping away a flood of tears now. Before adding, "That is a joke!"
1840 GMT: Rowling also in tears now.
1839 GMT: "Oh god," says Grint. "I'm really not very good at goodbyes. This has been such an emotional week." He thanks "everyone who's made these ten years the best of my life."
1837 GMT: Emma Watson's in tears, after thanking Barron and Heyman for being "like fathers to me".
1836 GMT: Radcliffe's been practising. "Hello everybody!" he says, with all the cheeriness of a well-practised stand-up comedian."Thanks for giving me a job," he says, adding, "I got very, very lucky when I was eleven."
1835 GMT: Yates dedicates the film to the fans.
1833 GMT: Fellow producer David Barron steps up now, and thanks, among others, his wife Sheila for "allowing me to spend more time with Harry than I've spent with her".
1832 GMT: "Thank you for making glasses, spectacles and red hair really cool," he says to Rowling. "Thank you for encouraging a generation of young people to read.
"Thank you for allowing us to make films from your books."
1831 GMT: After lots of thanking various people, David Heyman pays tribute to Watson, Radcliffe and Grint, who he says have grown into "wonderful young people". And finally, to David Yates' "brilliant vision".
1828 GMT: The three Davids: producer David Heyman, co-producer for the last film David Barron, and director David Yates take to the stage, after Meyer thanks some Warner Bros colleagues.
1825 GMT: Emma Watson, Daniel Radcliffe, Rupert Grint and Joanne Rowling are chatting behind him.
1824 GMT: That "very exciting" thing appears to be Barry Meyer, CEO of Warner Brothers. "Hello Trafalgar Square, and hello Harry Potter fans across the UK and the world!" he says.
1819 GMT: Alex Zane on the premiere's online live-stream is hinting that something "very exciting" is about to happen onstage at Trafalgar Square.
1815 GMT: Radcliffe and Watson's aides pushing them to stop signing autographs and head to the projection room...
1813 GMT: Emma Watson and Daniel Radcliffe still signing autographs like machines. One hopes they've taken precautions against Repetitive Strain Injury.
1808 GMT: England footballer and former captain John Terry has just walked up the red carpet, heading for Leicester Square, followed by film director Guy Ritchie.
1802 GMT: Rupert Grint is being asked about the long-awaited kiss with Hermione, again, and which his favourite of the films was, again. Trying and failing (just) not to look bored.
1759 GMT: Not everyone has been infected by the hysteria.
"There were a lot of very upset commuters trapped in the middle of it all," says Fred Rowson, who was down at Trafalgar Square a bit earlier. "And screaming. And loads of Italians worshipping a massive picture of Alan Rickman.
"It was basically like hell," he concludes.
1756 GMT: "I'll always be the ginger one," Rupert Grint tells AFP. "That's something that's going to stay." He seems pretty stoic about his fate.
1752 GMT: Both are thanking the fans, for what feels like the upteenth time tonight. More hugging.
1751 GMT: Rowling is asked if she would ever consider writing another Potter book. "I've always said 'Never say never, but I have no plans at the moment."
1750 GMT: Radcliffe pays tribute to Rowling for giving them an unusual amount of freedom. "She always understood that the books are untouchable," he says. The films couldn't compete with the books, "And they never tried to."
"I trusted them," Rowling agrees.
1747 GMT: In a long light green strapless dress covered in pink roses, Rowling and Radcliffe share a hug.
1746 GMT: Radcliffe's looking very smart in a three-piece grey suit, complete with tie clip. A TV presenter asks him what's got him through the filming, to which he answers, "A lot of Radiohead."
1744 GMT: And the other person everyone has been waiting for has now also arrived. Joanne Rowling, the creator of Potter's magical world, steps out wearing a light green dress. The Muggles are going crazy.
1742 GMT: "World Premiere of #HarryPotter outside @DCMS tonight," tweets Britain's Culture Secretary @Jeremy_Hunt. "Congrats to @wbpictures & @jk_rowling for over 10 years of British films at their best." No tweets about the closure of the News of the World newspaper, though, which is taking considerable media attention away from the premiere.
1740 GMT: And the man himself is here. Daniel Radcliffe is in the house.
1730 GMT: AFP's been talking to the film's screenwriter Steve Kloves on the red carpet. "Jo said to me the first time we met: I know the movies are not going to be like the books," he says. "All I ask you is to be true to the characters. That's what I've tried to do."
1724 GMT: Another nasty arrival -- Severus Snape, in the shape of Alan Rickman, looking much friendlier without the potions master's greasy black locks.
1723 GMT: French actress Clemence Poesy, who plays Fleur Delacour, tells AFP's Loic Vennin there is life for her beyond the series. "I'm not an orphan of Harry Potter," she says. "We knew it would end when we started."
1720 GMT: Helena Bonham Carter is talking about the part of the film where she gets to play Hermione playing her -- which she says was her "dream". Emma Watson gave her a guidebook on how to play the goody-two-shoes, she says.
1718 GMT: Williams is looking shabby, but pretty cool, with ruffled hair and a couple of buttons undone behind his tie. He gives a few words of Welsh for fans in Cardiff and beyond.
1712 GMT: Well, not quite. But a more low-key "goodie" -- Mark Williams, aka Arthur Weasley, has turned up.
1710 GMT: So a string of villains arriving -- could the hero himself be next to balance things out?
1709 GMT: And now Helena Bonham Carter is here. The Bellatrix Lestrange actress is wearing one of her typically idiosyncratic red carpet outfits: round sunglasses, and an absolutely huge pink rose pinned to the top of her head.
1707 GMT: Fiennes' fellow baddie Imelda Staunton, who plays Delores Umbridge, has just arrived and has started to slog through the autographs. Like Fiennes, she's also opted for a sinister black suit. Neither of them can quite get out of character, it seems.
1705 GMT: I take that back. Fiennes is staring around the red carpet in an ever so slightly Dark Lord-esque way.
1702 GMT: Voldemort is here -- but people are clamouring to get close to him, rather than screaming and fleeing. He Who Must Not Be Named -- in real life, Ralph Fiennes, is smiling as he moves through the crowds signing autographs. He couldn't seem less sinister.
1656 GMT: Robbie Coltrane's favourite thing about his character Hagrid? "He can look after and nurture animals that everyone else is terrified of."
1650 GMT: Emma Watson in the house. Wearing an incredible strapless pale grey dress with a wide, tutu-shaped skirt.
1646 GMT: The film's director, David Yates, says a late, poignant scene where Harry is walking through the woods to confront Voldemort is probably his favourite. "There's a sense of needing to sacrifice everything for his family and friends," he says.
1642 GMT: "Lots of people screaming, 'Rupert, Rupert," Reuben adds. "Presumably Grint, rather than Murdoch."
1641 GMT: "News of the closure of the News of the World has rippled through the press pack, momentarily distracting the British journalists from the red carpet," says AFP's Reuben Easey. The newspaper has announced it will print the last edition in its 168-year history on Sunday following a devastating scandal over phone hacking.
"The News of the World is to cease publication on the same weekend as Harry Potter finally defeats Voldemort," tweets @lord_liberace. "Life is mimicking art."
1637 GMT: Robbie Coltrane, better known as the loveable giant Hagrid, has arrived. A fraction of his on-screen size, but still larger than life, raising huge cheers from the crowd.
1634 GMT: Think the late arrivals must be tactical. Tom Felton, who's been here nearly an hour, is still signing autograph after autograph. His hand must be killing.
1632 GMT: Domhnall Gleeson, who plays Ron's big brother Bill, is also now doing the rounds. Gleeson's just been in the role for the last two films, taking over from Richard Fish who played the treasure-hunter in "Harry Potter and the Prisoner of Azkaban". His father, Brendan Gleeson, plays Alastor Moody.
1630 GMT: Bonnie Wright, aka Ginny Weasley, is stepping out of her car -- looking very elegant in a long-sleeved dusty pink number.
1625 GMT: Very strange seeing Narcissa Malfoy being so friendly. "That blonde hair is hell to upkeep," says Helen McCrory of her character. "So I'm happy to leave her on the screen."
1623 GMT: French actress Clemence Poesy, who plays Fleur Delacour, on the carpet...
1620 GMT: No sign yet of Daniel Radcliffe yet. The eponymous hero of the Potter series is only just back from New York, where he's playing the lead in the Broadway musical "How to Succeed in Business Without Really Trying". He's bound to make a big, late entrance.
1618 GMT: Identical Weasley twins James and Oliver Phelps are wearing different colour suits -- one's in black, the other's in ivory. Helpful.
1612 GMT: Veteran actress Julie Walters, who plays Harry's surrogate mother Molly Weasley, has just spotted herself on the enormous screen. "Shouldn't have eaten that pork chop," she says ruefully.
1612 GMT: Sounding a bit like her shy, oddball character, Lynch thanks her co-stars for making her feel "like part of the cast". It's a very sweet moment.
1611 GMT: Helen McCrory, who plays Draco Malfoy's mother Narcissa, is looking stunning in a red velvet dress.
1609 GMT: Evana Lynch plays tribute to her "quietly strong" character, Luna Lovegood. Or, as TV presenter Alex Zane said earlier, "Luna Lovejoy" -- drawing much derision from uber-fans on Twitter.
1606 GMT: The Weasley twins, James and Oliver Phelps, look suspiciously dark-haired. Have they got rid of their famous ginger locks? It's one way to put a stop to all the harassment in the street, I suppose.
1603 GMT: Tom Felton, who plays Potter's arch-nemesis Draco Malfoy, declares Gambon as "the godfather" of the cast. Gambon himself says the whole experience has been "overwhelming".
1558 GMT: And now Michael Gambon, who plays Hogwarts headmaster Albus Dumbledore, is stepping out of his car. A highly respected theatre actor he may be, but he's not quite the same without the big white beard.
1554 GMT: Evana Lynch, aka Luna Lovegood, has arrived in a short white number and is signing a few autographs.
1553 GMT: Lots of fans at Trafalgar Square waving copies of the books, hoping to glean a few signatures. Pity the ones wielding the later, weightier ones.
1552 GMT: Ron Weasley actor Rupert Grint's been talking to the BBC. "It's hard to really believe. It hasn't really sunk in. It's unreal," he says. "It's so overwhelming. It's really strange.
"These last few months I've been in a bit of denial, I think, accepting the fact that it really is over. When I saw the posters in capital letters, 'It all ends', it really does imprint that on the mind. I will miss this. It's been amazing.
"I was just a big fan of the books and just a normal kid and very suddenly, I was in this crazy world and completely out of my depth!
"It will be great to see everyone again because it's been a while since we last saw each other. It will be a big reunion. Maybe a bit emotional."
1550 GMT: "I've been reading the books since elementary school," Tiffany Milow, a 22-year-old from Dallas in Texas, tells AFP's Nick Morrison. "We used to bring them to book swap, and then I moved on to the films. I'm torn apart that this is the last one -- I'm devastated."
1548 GMT: Tom Felton, better known as Draco Malfoy, has arrived with an (as yet) unknown lady in a very dramatic tiered white dress.
1541 GMT: Matthew Lewis, aka Neville Longbottom, and Lucius Malfoy actor Jason Isaacs now here and chatting to fans on the red carpet.
1538 GMT: Kay Miller, 42, came down by coach from Stirling in Scotland at 7am yesterday. She is wearing a fetching Griffindor scarf and hat.
"There's a fantastic atmosphere down here," she says."It's been very lively despite the rain!
"I've met people from all around the world -- there are fans here from Mexico, Australia, Italy and Germany.
"As well as the main stars, I'm hoping to see Jason Isaacs, Alan Rickman and Ralph Fiennes on the red carpet - and I really want complete satisfaction from the film. I want to have the whole saga wrapped up so that we're not left hanging!"
A sign of a true fan, she is also sporting a (temporary) Slytherin tattoo on her shoulder and a time-turner -- a pendant which allows time-travel -- around her neck.
1534 GMT: James and Oliver Phelps, the identical twins who play Fred and George Weasley, will be dressed very practically this evening, according to the Guardian.
"The pair will be decked out in water-resistant three-piece suits designed by David Brooke of Mathieson & Brooke tailors," the newspaper says.
1630 GMT: Interviewed on the red carpet by TV presenter Alex Zane, Grint is asked about that long-awaited kiss with Emma Watson. "It's a kiss that has been building up from the first films," he says. "There was a lot of pressure on us to make it a big moment."
1527 GMT: Grint's looking quite natty in a black suit and tie. The crowd's gone crazy.
1525 GMT: Sorry, that should have said Rupert Grint. Grint gets very tired of being called Ron. Though as he told the Guardian rather wearily this week, "I answer to it. I turn around to it in the street."
1523 GMT: Ron Weasley is here!
1512 GMT: Voldemort's lost the weather war. After hours of drizzle, the sun's come out.
1507 GMT: Good news for those in Trafalgar Square hoping to speak to, or (gasp) even touch Mr Potter himself. Daniel Radcliffe -- who wasn't at yesterday's press conference with co-stars Rupert Grint and Emma Watson -- has warned journalists he'll be spending most of his time this evening with his fans.
1502 GMT: A makeshift Diagon Alley has been set up on Charing Cross Road between Trafalgar Square and Leicester Square, says AFP's Loic Vennin. Shops are selling cauldrons, pumpkins, and even a branch of wand-makers Ollivander's has sprung up.
Down on Trafalgar Square itself, the placards give a fairly good summary of the fans' mental state. "We queued for 48 hours because we're potty about "Potter," reads one. "HP is over. See you in therapy", says another.
1500 GMT: Welcome to AFP's live coverage of the world premiere of "Harry Potter and the Deathly Hallows -- Part 2", the action-packed finale to the boy wizard's epic film series. We'll bring you minute-by-minute updates from London's Trafalgar Square, which has been rammed for days now with fans hoping to catch a glimpse of the stars. Stay tuned for the first celebrity arrivals...
