After a decade of contentious legal debate, the case of accused Hacker Gary McKinnon could finally be over with the announcement that he will not face charges in the UK.

Director of Public Prosecutions (DPP) Keir Starmer QC concluded that there was no likelihood of McKinnon being convicted for crimes carried out against servers in the US.

"The potential difficulties in bringing a case in England and Wales now should not be underestimated, not least the passage of time, the logistics of transferring sensitive evidence prepared for a court in the US to London for trial, the participation of US government witnesses in the trial and the need fully to comply with the duties of disclosure imposed on the CPS, said Starmer in a statement.

"The prospects of a conviction against Mr McKinnon which reflects the full extent of his alleged criminality are not high."

In October, a longstanding US request to extradite McKinnon was turned down by Home Secretary Theresa May, who cited a significant risk to his health.

The move is not a surprise given that the UK declined to prosecute McKinnon in 2009, despite an indication that he would pleade guilty to breaking the Computer Misuse Act if allowed to stand trial in the UK.

Although McKinnon will never be able to visit the US for fear of arrest (or any other country willing to detain him pending extradition), the latest announcement brings a practical if not formal end to the legal actions against him.

His story was as extraordinary as the legal process turned out to be drawn out, taking in successive US administrations, three British Prime Ministers and six Home Secretaries.

The US accused him of penetrating and causing damage to at least 97 US military and NASA servers between February 2001 and March 2002 and wanted to try him in the US for his alleged crimes.

But from the start the case had a political as well as legal dimension; successive appeals to stop this process under a 2003 extradition treaty failed until the ball dropped into May’s court before she could dodge it.

The US response to the decision is likely to be cool in a country where convicted cybercriminals can usually expect the tough justice of a long sentence.