Last night's episode saw Richie's Alfie confronting his wife Kat (Wallace) in her secret bedsit, before eventually discovering that she was having an affair with Derek Branning (Jamie Foreman).
Richie explained that filming the scenes with Wallace in such close proximity was very "claustrophobic".
"It's very rare you get a 15-minute scene with two people in one room," he told BBC News.
"We don't usually get a chance to rehearse but for this particular episode we spent a lot of time - myself and Jessie and the director [Karl Nielson] - just going over stuff, finding out where the emotions were, who was the victim, who was on the offensive, who was on the defensive, and that's what we tried to do.
"We were in a tiny space which was purposely built for these episodes, so filming it was quite claustrophobic. It's so unlike upstairs in the Vic, where you're familiar with it.
"This was one square room. There was nowhere to hide, you were on show - every blink of the eye, every look, every frown, every sigh, if you're looking angry, it's there to be seen, you're naked to it. I really love that."
He added: "I love that because you work hard to try and be as good an actor as you can and then you're given an opportunity by the BBC and by EastEnders to step up to the mark.
"Lorraine [Newman, EastEnders Executive Producer] believing that two actors could do that - it's a bit of a pressure on your shoulders, but me and Jessie loved it."
Looking ahead to the future for Alfie, Richie said that a "love triangle" was highly likely.
"There's a great story coming up - I had a meeting about it today, which I cannot tell you about! But it's another big storyline. In the meantime, I think we're going to get into a love triangle - Roxy thinking that Alfie's on the rebound."
He continued: "I think Roxy brings out the best in Alfie. I was kind of reluctant that he would be straight in with Roxy, but I can see why he does it.
"He needs to be with someone. He needs someone he can be there for. He needs a shoulder to cry on. But at the same time he hasn't got Kat. It's slightly dangerous."
Shane Richie also revealed that he did not know the identity of Kat's lover for a long time.