As for why she believed his involvement got such a strong response, she said he was "a trusted voice".
"At the time he was in people's living rooms every day. He was very trustworthy and that's what we identified about him when we were talking about perhaps approaching him, that he was a trusted face and a trusted voice and he seemed calm and assured and people listened when he spoke.
"I think that was the key thing. People did listen when Greg spoke."
She said it wasn't that long ago when no one, particularly celebrities, wanted anything to do with the foundation.
"We're not so far removed from the days where no one would talk about it, or be associated with a mental health campaign.
"I've worked here for six years and initially no one wanted to be associated with the mental health foundation."
She said he never spoke of his own battles publically, but the campaign, run the Health Promotion Agency, was more to break down barriers around the stigma of mental illness.
"People who experience mental distress and mental illness, one of the biggest barriers to recovery is being excluded, being stigmatised and discriminated against the and whole purpose of the Like Minds cam pain was saying that together we're a big part of the recovery process."
The latest figures from the Ministry of Health show that an estimated 640,000 adults, aged 15 plus, were defined by their doctor as having depression for the year 2016/17.