Julian Assange is anticipated to plead guilty to a felony charge linked to his alleged involvement in a major leak of classified information, according to court documents filed on Monday.

WikiLeaks founder Julian Assange was released from a British prison and began his journey back to Australia on Monday, following the conclusion of his 12-year legal battle against extradition to the United States.

The controversial figure has spent the last five years in a high-security prison in southeast London, preceded by nearly seven years confined to the Ecuadorian embassy in London to evade arrest, which could have resulted in life imprisonment.

On Monday, Assange, aged 52, agreed to plead guilty to a felony charge linked to his alleged involvement in one of the largest breaches of classified US government materials. His whistleblowing website published close to half a million secret military documents concerning the US wars in Iraq and Afghanistan.

The plea deal marks the end of a protracted legal saga, allowing Assange to avoid imprisonment in the US and eventually return to Australia as a free man. However, he is required to appear in court in a remote US territory in the Pacific before departing.