A police officer has accidentally revealed plans to seize Julian Assange "under all circumstances" if he steps outside the Ecuadorian embassy.
A document carried by the officer made clear their determination to arrest the WikiLeaks founder should he leave the building.
The document, captured by Press Association photographer Lewis Whyld, was recorded at a briefing and appears to order police to make the arrest if Mr Assange attempts to leave in a diplomatic bag or vehicle.
A Scotland Yard spokesman said: "The document is one officer's notes from a briefing. Our objective is to arrest Julian Assange for breach of bail. Under no circumstances would any arrest be made which was in breach of diplomatic immunity."
Mr Assange, who has been in the building for two months, is wanted for questioning in Sweden over claims of sexual assault. He is refusing to travel to Scandinavia amid fears he will be extradited to the United States over his controversial website. Ecuador granted the Australian political asylum last week.
The UK government has made it clear Mr Assange, who denies the allegations, will be arrested if he steps outside the embassy after jumping bail.
Ambassadors from several South American countries have visited the embassy on Friday.
An embassy spokesman said: "This display of support for the Ecuadorian Government by South American ambassadors is a clear indication of the level of support Ecuador has amongst countries in America and a clear statement opposing the UK Government's threats against the integrity and sovereignty of its embassy in London."
The British Government has threatened, under a 1987 Act, to enter the embassy and arrest the 41-year-old, but Foreign Secretary William Hague has said there is no intention to "storm" the building.
Ecuador's president has said the diplomatic row "could be ended tomorrow" if Britain gave the activist safe passage to South America. Rafael Correa said: "This could end tomorrow if the UK grants safe passage, or it could go on for months and years if Mr Assange can't leave the embassy of Ecuador in London."