“The proposition that there were leaks in the Australian Department of External Affairs from the end of the war, dramatically revealed by the defection of Vladimir Petrov in April, 1954, has commanded great attention and has come to be generally accepted,” is stated (p. 92) by Wayne Reynolds in his 2000 book Australia’s Bid for the Atomic Bomb at the start of a chapter called “The ‘problem’ of Australian security.” The Petrov Affair, as it is known, has always vaguely fascinated me, but I’ve never delved into it and, after reading Reynolds’s bewildering chapter, I don’t intend to dig in now. The impact of the defection on my book is tangential and comes down to a couple of general matters that can remain ambiguous: Australia’s shift from a U.K. focus to a U.S. focus over the 1950s and 1960s; and the 1950s exit, stage left, of original atomic star Marcus Oliphant from the nuclear energy scene. Neither really matters to me, they’re just something that happened off to one side.
If you are interested, the Wikipedia entry on the Petrov Affair seems quite thorough, and a couple of historical book accounts seem to be interesting and comprehensive.