Assange extradition case is heard by Supreme Court.

BBC- Wikileaks founder Julian Assange has started his latest legal action to try to block his extradition to Sweden at the Supreme Court in London.

The appeal is based on whether the Swedish prosecutor who issued the European Arrest Warrant against him had the judicial authority to do so.

Mr Assange is wanted by the Swedish authorities for questioning over alleged sex offences, which he denies.

Judgement is expected to be reserved to a later date.

The key legal question for the seven judges is whether the prosecutor who issued the arrest warrant had the judicial authority to do so under provisions of the 2003 Extradition Act.

Mr Assange's lawyer, Dinah Rose QC, said it was "a matter of fundamental legal principle" that the person issuing such a warrant was both independent and impartial.

But she said the Swedish prosecutor was a party in the Assange case and therefore was not either of these things.

Ms Rose submitted: "Since the Swedish prosecutor cannot fulfil those conditions, she is not a judicial authority and not capable of issuing a warrant for the purposes of he 2003 Act."

The arrest warrant itself was therefore invalid, she said.

Dozens of supporters gathered outside the Supreme Court to greet Mr Assange as he arrived for the hearing.

The 40-year-old Australian, who remains on conditional bail in the UK, claims the allegations against him are politically motivated.

He is accused of raping one woman and "sexually molesting and coercing" another in Stockholm in August 2010.

Mr Assange's Wikileaks website published a mass of material from leaked diplomatic cables embarrassing several governments.

The High Court previously approved his extradition, a decision that Mr Assange argues was unlawful.

In December, two High Court judges, Sir John Thomas and Mr Justice Ouseley, decided that Mr Assange had raised a question on extradition law "of general public importance" and allowed him to ask the Supreme Court for a final UK ruling.

Later that month, a Supreme Court spokesman said its justices had agreed to hear the case "given the great public importance of the issue raised, which is whether a prosecutor is a judicial authority".