Hart is on a season-long loan from Manchester City and had his Toro presentation yesterday.
Petrachi stated: “We were looking to take an Italian goalkeeper in Viviano and an agent, when it became clear that the conditions weren't there, his agent told me he could give me a gem and there was a very, very good English player: the goalkeeper Hart.
“Vigorelli told me he knew Hart's agent, who told him the lad wanted to have an experience abroad and that Italy would be a pleasant destination.
“I responded to Vigorelli, 'maybe', but there and then I didn't think we'd be able to complete the deal.
“However, I immediately said, 'we're talking about a very important goalkeeper and if the news comes that Hart can leave Manchester City then many clubs will try to take him, otherwise we'll pursue the deal and you can get me to talk to his agent'.
“When we were able to talk to Hart, his agent made me realise that Joe was interested in the idea of playing in Turin. I then put him in touch with the Coach.
“Mihajlovic asked him if he really believed in Torino and with what humility would he face this kind of experience because Torino would've been pleased if he came, but only with the right mindset in order to really lend a hand.
“Hart gave his total availability, and thus the Coach told me that if the conditions were there, we needed to get him.
“Therefore, I immediately called President Cairo, who told me he'd be a great opportunity, and I had to try and do the best to conclude the deal, of course without the headlights on, because if it had leaked into the Press, we wouldn't have been able to sign Hart.
“I think in the end, they were all very professional, although on the home stretch, the news came out in England and other clubs including Sunderland tried to get him, but Hart had already given us his word that he'd come to us."