Innocent of any commercial motive, McDonald went on to tell the show's 2.6 million viewers how lovely Wallace Arnold trips are.
It just so happened that Wallace Arnold's PR man, Brighter PR managing director Steve Dunne, was one of those tuned in to BBC 2 at the time.
Dunne, we hear, has since phoned McDonald's agent and offered her free tours on Wallace Arnold - if she writes some copy about the company for a national newspaper.
'We thought that since she likes our coaches so much, why not?' says Dunne. 'We are trying to get a younger audience interested in Wallace Arnold - and what better way than Never Mind the Buzzcocks and McDonald?'
Dunne is still awaiting a response.