Quoting from the Wikipedia article on G. H. Hardy (emphasis mine):
Starting in 1914, he was the mentor of the Indian mathematician Srinivasa Ramanujan, a relationship that has become celebrated.[3][4] Hardy almost immediately recognized Ramanujan's extraordinary albeit untutored brilliance, and Hardy and Ramanujan became close collaborators. In an interview by Paul Erdős, when Hardy was asked what his greatest contribution to mathematics was, Hardy unhesitatingly replied that it was the discovery of Ramanujan. He called their collaboration "the one romantic incident in my life."[3][5]
I am curious to read this interview of one giant by another. After some Internet search, I found that the paragraph is taken from an encyclopedia entry on NationMaster.com, but unsurprisingly it cites no references for the said interview.
Have you heard about or read this interview before? Is it available online?
References.
[3.] The Man Who Knew Infinity: A Life of the Genius Ramanujan.
[4.] 20th Century Mathematics – Hardy and Ramanujan.
[5.] Freudenberger, Nell (16 Sep 07). Lust for Numbers. The New York Times.
I am including the references because these are referred to in the quoted paragraph. However apparently — this is just my guess — none of them mentions the interview.
Best Answer
I've found the source of this interview.
It's in Paul Erdos' biography by Paul Hoffman, " The Man Who Love Only Numbers"(1998). Starting from page 78, the book describes Erdos left Hungary for Cambridge in 1934 due to the raging Hungarian Fascism. It was at Cambridge, the second day of his arrival, that he met G. H. Hardy, and inquired him about Ramanujan.
The quote "Erdos asked Hardy what his most important contribution to mathematics was. 'The discovery of Ramanujan,' " appeared at the bottom of page 82.