Speaking over Zoom with O'Carroll, her legal representative, the pair give an overview of events leading up to the 2018 judgement - and the very real lessons they learned along the way.
They share their accrued knowledge on how to take a court case against institutional issues like the CervicalCheck scandal, and answer the frequently asked questions of the case.
"In January of 2018, I'd just been diagnosed with terminal cervical cancer. Three months previously, I had a sit-down with my gynaecologist, who had wanted to have a chat with me about an audit that had taken place in CervicalCheck," says Phelan.
"It came out of nowhere, and at a time when I didn't know my cancer was back... I was happy to park it at the time because I was happy to be cancer-free.
"But while I was waiting for a biopsy in a treatment room, bored off my head, I looked through my file and found a report about my file. I knew there was more to this audit than what I was told. I knew there was a chance I could have been misdiagnosed, and I sought legal representation.
"I never thought three years later that it'd set off one of the largest legal scandals in the history of the State."
O'Carroll and Phelan set out an overview of the rollout of the CervicalCheck system in the wake of a backlog of cases in the 2000s. The backlog led to a tender for outsourced lab work, landed by a US firm.
They explain the resultant issues, including slides being further outsourced to secondary labs, before getting into Phelan's case.
"The advantage of being the first case is that the HSE didn't know what was coming," says Phelan. "We got documents that, had they known what was coming, they wouldn't have released.
"They were confident I'd sign a non-disclosure agreement - they weren't banking on me being as bolshy and as stubborn as I am."
"The day I stood on those court steps, reading that statement, I didn't think I'd be here three years later, still fighting for answers for women, and myself, and to improve outcomes."
The immediate aftermath of the court case - including the headline-grabbing €2.5m settlement - is highlighted.
Phelan speaks about the importance she knew her words carried. Preparation for interviews was all-important, but so too was an even keel, she says.
"I had to be measured. It was a very difficult balancing act for me, because I could have [gone on the air] and slammed the whole health service, told women not to go get their smears, but I didn't, because I knew women would listen to me, and not get their smears.
"I know how bad this cancer is, and there's no cure for it, so I didn't want more women being diagnosed, I want less, in fact.
"It was all about exposing the harm, and working with them to improve the system."
The episode is streaming in the player above, and available for streaming on Spotify.