British spies will find out later if they are to be charged over alleged complicity in the torture of terror suspects.
Several MI5 and MI6 agents are understood to be at the centre of criminal investigations into the treatment of former detainees including UK resident Binyam Mohamed.
Prisoners at Guantanamo Bay have claimed British security and intelligence officials colluded in their torture and abuse while they were held at the controversial detention centre.
Both the police and Keir Starmer, the Director of Public Prosecutions (DPP), are due to issue a statement on the matter later.
The Daily Telegraph is reporting sources who say Scotland Yard and the DPP have concluded there is no case to answer following the four-year investigation.
An inquiry into British complicity in torture and rendition is due to begin in the wake of the police investigation.
Foreign Secretary William Hague has previously stressed the Government's commitment to "drawing a line" under the alleged involvement of intelligence agencies in the torture of terror suspects overseas .
Human rights groups and lawyers are refusing to give evidence or attend any meetings with the Gibson inquiry team because it does not have "credibility or transparency".
A number of British Muslims have complained that they were questioned by British agents after being tortured in Pakistan, Bangladesh, Afghanistan and Guantanamo.
Others say they were tortured in places such as Egypt, Dubai, Morocco and Syria, while being interrogated on the basis of information that could only have been supplied by the UK.
The Government has made payouts to 16 former detainees at Guantanamo to pave the way for the Gibson inquiry
Among them is said to be Binyam Mohamed, who was granted refugee status in Britain in 1994, travelled to Pakistan in 2001 and was arrested there a year later on suspicion of involvement in terrorism, before being "rendered" to Morocco and Afghanistan.
After being subjected to alleged torture by his US captors, he was sent to Guantanamo Bay in 2004.
Charges were later dropped and he returned to Britain in 2009.
The charging decision comes days after human rights campaigners condemned the US government's ongoing failure to close Guantanamo, 10 years after the arrival of the first prisoners.