Now he is suddenly at the core of one of the soap's biggest storylines, as the twin brother of Lucy, who was found murdered last month. And with that comes lots of questions over who might be responsible for the mysterious death.
"I don't know who it (the culprit) is - none of the actors do, as far I know," says Hardy. "There is a big veil of secrecy and some censored scenes that I haven't been able to read."
He knows his on-screen father Ian, played by Adam Woodyatt since the show began 29 years ago, is hiding something. "But I don't know what it is and Adam won't tell me - as much as I ask him!" he adds.
The storyline is set to run for months and the perpetrator will not be revealed until next year, but Hardy does not think it will turn out to be Peter.
"I don't think he has enough motive and if it came out that it was him, I would wonder where it has come from," he says. "With the facts we know so far, it would be a case of him being some psychopath that has been pretending to be nice for his entire life."
His part in the soap over the last six months has seen the 23-year-old recognised much more in public and he has taken to dressing differently as a disguise - "but it doesn't seem to work".
"I have tried hats, sunglasses," he says. "I come in to the set (at Elstree Studios) on the train and I'm usually there with a lot of labourers, so try and dress up like one of them."
More often than not, though, he is spotted by local school girls. "They say, 'Peter, Peter, Tell me what's happening!"'
Although he claims he does not pay attention to ratings, he has sensed a resurgence of interest in the soap.
"The public opinion seems to be it is back on track and my friends back home in Bournemouth are watching it again, not because of me - because they didn't start watching it when I joined - but because of the storyline."
Filming the aftermath of Lucy's death has been an emotional slog.
"But I'm glad to have the challenge," says Hardy, who primes himself for scenes by thinking about his own family being in that situation.
"I don't have a sister, but I try and think about me and my brother or my mum and dad. Sometimes, you don't feel it as much or it doesn't come as easily, so you have to really dig deep and think of memories that have been upsetting to try and get that sort of emotion."
He believes Woodyatt has "a gift" for accessing those feelings so quickly.
"We don't really talk much before the emotional scenes, because he does not like to do it too many times," Hardy says.
"He gets upset just reading it, so wants to do one take and it's done. But it can take me three or four goes to get to that place, and he is very supportive of that."
With the emotive storyline only now unravelling, it must be difficult, at times, not to get overwhelmed.
"I try and take five minutes out at the end of day to mentally switch off," says Hardy. "Then I can think, 'Right, that's it. I'm not taking it home with me'."