Julian Assange has been granted leave to mount a fresh appeal against his extradition to the US on charges of leaking military secrets and will be able to challenge assurances from American officials on how a trial there would be conducted.

Two judges had deferred a decision in March on whether Assange, who is trying to avoid being prosecuted in the US on espionage charges relating to the publication of thousands of classified and diplomatic documents, could take his case to another appeal hearing.

On that occasion, Dame Victoria Sharp and Mr Justice Johnson ruled he would be able to bring an appeal against extradition on three grounds, unless “satisfactory” assurances were given by the US.

The assurances requested were that he would be permitted to rely on the first amendment of the US constitution, which protects freedom of speech; that he would not be “prejudiced at trial” due to his nationality; and that the death penalty would not be imposed.