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Business Insider overheard the conversation outside the Westminster Arms on Thursday. The Westminster Arms is a pub in Westminster that is popular with Parliamentary staffers.
Guardian columnist Milne has found himself thrown in at the deep end after Jeremy Corbyn made him his comms chief last month.
Milne doesn't have any experience in communications, so it's not surprising that he's keen to pick up some tips.
Milne asked Kuenssberg, who is the most senior political journalist at the BBC for advice on everything from the upcoming by-election in Oldham to broading Jeremy Corbyn's appeal with the public.
Kuenssberg, who in her job at the BBC must treat news stories with "due impartiality," obliged Milne with answers for over an hour, telling him what she would do if she were him.
Kuenssberg didn't hold back as they discussed trouble that Momentum, the grassroots organistation that supports Corbyn, is having finding broader support among the public. "If you want to communicate with a nation you have to actually do it. You can't just call everybody b*******," she sternly informed Milne.
It's fairly normal for journalists to have off-the-record frank discussions with comms staff, but they usually do it somewhere a little bit more private. It seems Milne has a steep learning curve ahead of him still.