The founder of the whistle-blowing website Wikileaks, Julian Assange, has been arrested by the Metropolitan Police.
The 39-year-old Australian denies allegations he sexually assaulted two women in Sweden.
Scotland Yard said Mr Assange was arrested on a European arrest warrant by appointment at a London police station at 0930 GMT.
He is due to appear at City of Westminster Magistrates’ Court later.
Mr Assange is accused by the Swedish authorities of one count of rape, one of unlawful coercion and two counts of sexual molestation, alleged to have been committed in August 2010.
If the district judge rules there is a prima facie case to be answered by Mr Assange, and the arrest warrant is legally correct, he could be extradited to Sweden.
But the process could take months.
Police contacted his lawyer, Mark Stephens, on Monday night after receiving an European arrest warrant from the Swedish authorities.
An earlier warrant, issued last month, had not been filled in correctly.
Mr Stephens said his client was keen to learn more about the allegations and anxious to clear his name.
He said: “It’s about time we got to the end of the day and we got some truth, justice and rule of law.
“Julian Assange has been the one in hot pursuit to vindicate himself to clear his good name.”
Mr Stephens said Mr Assange had been trying to meet the Swedish prosecutor in various ways to find out the details about the allegations he faces.
Mr Assange has come in for criticism in the last week for the revelations made on Wikileaks.
On Monday, Foreign Secretary William Hague criticised the website for publishing details of sensitive sites, including some in the UK, saying they could be targeted by terrorists.
Former US vice-presidential candidate Sarah Palin has described Mr Assange is “an anti-American operative with blood on his hands”.
Wikileaks was forced to switch to a Swiss host server after several US internet service providers refused to handle it.
It has also come under cyber attack and several companies, including PayPal and Amazon, have refused to supply it.
Mr Assange is expected to appear before a district judge at City of Westminster magistrates court before 1230 GMT, unless special permission is given for a later hearing.
City of Westminster deals with most extradition cases but there are huge differences in the time it takes.
Some cases, such as the extradition of computer hacker Gary McKinnon, have been going on for years because of legal challenges.
But extradition can be extremely swift if the accused waives his legal rights.
Mr Assange is an Australian citizen and his supporters have written an open letter to Australian Prime Minister Julia Gillard asking her to protect him.
One of the signatories, prominent barrister, Julian Burnside QC said: “First and foremost Julian Assange is an Australian citizen who is entitled to the protection of his country and does not deserve to be betrayed by his country.
“Julia Gillard has been making it virtually impossible for Assange to return to Australia where he is entitled to be. And she has even threatened to cancel his passport. That is an outrageous stance to take.”