Julian Assange is another step closer to extradition after a High Court decision. The WikiLeaks founder, who is considered a fugitive by the US government, has avoided going on trial in the US for years.

He is wanted over an alleged conspiracy to obtain and disclose national defence information relating to the Afghanistan and Iraq wars. British courts have previously blocked attempts to extradite Assange on the grounds he may be subjected to highly restrictive prison conditions.

Washington authorities have given formal assurances that he would not face those strictest measures either pre-trial or post-conviction unless he committed an act in the future that required them. Now the American government has won a legal bid to overturn a judge’s decision not to extradite him on the basis of those commitments.

After a two-day hearing in October, the Lord Chief Justice Lord Burnett, sitting with Lord Justice Holroyde, ruled in favour of the US on Friday.

Lord Burnett said: “That risk is in our judgment excluded by the assurances which are offered. It follows that we are satisfied that, if the assurances had been before the judge, she would have answered the relevant question differently.”

He added: “That conclusion is sufficient to determine this appeal in the USA’s favour.”

• A Tell report