By Nesta McGregor and Jonathan Blake
Jacko fans pull out their best moves
Metal detectors, bag scanners and large numbers of security guards. It can only mean Michael Jackson's in town.
Inside the O2 Arena giant video screens flash images of Jacko while coffee shops are packed with fans.
A lucky 150 have managed to get passes for Michael's comeback news conference.
Gemma's from Liverpool. She has Jacko's name tattooed around her wrist. She said: "I love him and that's my way of showing it."
Posters advertising Michael Jackson's comeback gigs have already started to appear in London.
They mention 10 concerts in July and encourage fans to register for more info online.
However, the official announcement on the gigs isn't due until 4pm on Thursday and as yet no tickets are on sale.
Posters promoting the gigs have started to go up
Jackson is expected to reveal a summer residency at London's O2 arena that could last as long as 30 nights.
The shows would mark a major comeback for the star, but many claim he's only playing to rebuild his battered finances.
Fans have been arriving at the O2 all day. There've been huge cheers from them every time they hear a noise as they think Michael's already in the building.
Danielle's 18 and from Romford. She thinks Michael will go down in history no matter what happens.
She was close to tears as she told Newsbeat how she listened to his Greatest Hits again this morning and reckons he'll be moonwalking all his life.
Asked what she would tell Jacko if she had the chance she said: "Keep doing what you do because you'll always be a legend to me."
Fans at hotel
Jackson's thought to be have been in London for several days and some fans gathered at his hotel hoping for a glimpse.
Ann-Marie and Danielle Gom - mother and daughter - were outside the Lanesborough.
"I just think he's amazing. I can't wait until the summer when he's going to surprise all these sceptics that think he hasn't got it in him any more," said Ann-Marie.
Bethany hoped to get a glimpse of the secretive star
Bethany Geach, 18, said she was looking forward to seeing her idol: "All Michael Jackson shows are going to be a big spectacle. There'll be dancers, pyrotechnics, all that kind of stuff."
However, the star's last performance, at the World Music Awards in London in 2006, lasted just a few seconds. Many thought he'd had it then.
Anne-Marie and Danielle were at the ceremony and disagree: "You could see he wasn't 100%, but he still tried to pull it out the bag and I thought he did really well."
Some fans though, do acknowledge Jackson's comeback performances are unlikely to be up to the standard of his previous live shows.
Rhianan said she was thinking about going to every concert
"Sometimes it's more about the experience and everyone else being there, the 'Michaelmania'," said Rhianan Adam, 26, who'd come to the hotel on a break from work.
"I've been a fan since I was five… and I've waited 12 years for him to perform again. I thought his career was going to be over."
Rhianan said she was planning to see as many shows as she could: "I was considering how much my credit card could handle, whether I could go and see 30 dates and go to every after show party."
Michael Jackson may not sell as many records as he used to, but fans like Rhianan say it's unlikely his comeback shows will be anything less than a sell-out.
She said: "He's inaccessible, the one person on the planet who's completely a mystery, no-one gets access to him, he's just untouchable. He's got that real star factor."