no duff
other.— «L/Cpl Steven Jones, 25—an Army passenger on the plane—yelled, “No duff, no duff, we are on fire, we are on fire,” before communication was lost. “No duff” is a military term used to indicate a real emergency instead of a drill.» —“http://www.thesun.co.uk/sol/homepage/news/campaigns/our_boys/article988834.ece” by John Coles Sun (United Kingdom) Apr. 2, 2008. (source: Double-Tongued Dictionary)
We had a similar expression when I was a teenager in Montreal in the early 1970s. “No guff” meant “I’m not kidding you” or “I’m telling you the truth”.