"Mark made a passing comment, something like 'scuttlebutt floating around for a while about the mayor having a skeleton in his closet; if there is a skeleton I hope that his wife and children know because families are always the victims in these sort of things'. I laughed, saying, 'I'm sure it isn't correct,' and he agreed with me.
"It was a generic conversation between him and me and I deeply regret using his name in a later conversation with the mayor's chief of staff."
A source inside the Brown camp said the word from Mr Mitchell was enough to say to Mr Brown that he needed to tell the mayoress, Shan Inglis, about the affair.
Mr Mitchell said last night that he accepted the apology.
"She didn't have to do that but certainly I appreciate it. I know my wife does as well."
• Exclusive in tomorrow's Herald on Sunday: Interview with Luigi Wewege.