When WikiLeaks first claimed in a tweet that it was assisting NSA whistleblower Edward Snowden's "political asylum in a democratic country" there was one detail that apparently confirmed its involvement – that Snowden was travelling with a person whose surname was Harrison.

Sarah Harrison – a staff member for more than two years – has become one of Julian Assange's closest advisers since first working with the group as an intern on the publication of the Afghan war logs.

Direct intervention in Snowden's case marks a departure in practice for WikiLeaks – which has previously stressed its arms-length relationship with sources – but is consistent with the organisation's world view on protecting whistleblowers. It also cements its reputation as a thorn in the side of the US and UK governments.

Speaking to the Sydney Morning Herald from the Ecuadorean embassy in London, Assange said: "Owing to WikiLeaks' own circumstances, we have developed significant expertise in international asylum and extradition law, associated diplomacy and the practicalities in these matters.

"I have great personal sympathy for Ed Snowden's position. WikiLeaks absolutely supports his decision to blow the whistle on the mass surveillance of the world's population by the US government."

Harrison may seem a strange choice to accompany Snowden since, unlike several people close to WikiLeaks – most notably human rights lawyer Jennifer Robinson – she has no legal qualifications or background. But Assange's group has also offered the support of its legal director Baltasar Garzón, the former judge who ordered the arrest in Spain of former Chilean dictator Augusto Pinochet.