On 3 April 1954, Petrov defected in Sydney. He was the most senior-ranking Soviet spy to defect to the West since the 1930s. Two weeks later his wife, Evdokia, an embassy cipher clerk and MGB officer, also defected after dramatically being freed from armed Soviet couriers by Australian security police at the Darwin airport. Not surprisingly, the Petrov defections caught the interest of the Western counterintelligence community, resulting in the closing of the Soviet embassy in Canberra and the withdrawal of the Australian embassy staff from Moscow.
Australian Prime Minister Robert Menzies promptly established the Royal Commission on Espionage, which convened for 126 days, examined 119 witnesses, received more than 500 exhibits, and published almost 3,000 pages of transcripts. The exhibits included the controversial Petrov Papers handed over at the time of Petrov's defection. Although many on the Left alleged these to be forgeries and that the defection itself was a political conspiracy, the declassified Venona decrypts confirmed the authenticity of the documents in 1996. The royal commission uncovered evidence of successful Soviet espionage in Australia during 1945–1948 but could not initiate prosecutions without compromising the Venona operation. Petrov's revelations caused an uproar not only in Australia but also in Great Britain, as he provided new material, leaked to the British press by MI5 officers, concerning the flight, defection, and whereabouts of the missing British spies Guy Burgess and Donald Maclean.
Petrov received a new identity, Sven Allyson, and lived in a safe house in the Melbourne suburb of East Bentleigh, where he died in a nursing home on 14 June 1991.
Thwaites, Michael. Truth Will Out: ASIO and the Petrovs. Sydney: Collins, 1980.; Whitlam, Nicholas, and John Stubbs. Nest of Traitors: The Petrov Affair. Brisbane: Jacaranda, 1974.