Never had Nigel Farage been forced to sit through a more ferocious tirade. Well, not very often, anyway; and it wasn't over. The "biggest racism I've seen in British politics... hatred reaching a truly astonishing level." Farage blinked, and drew a deep breath.
We were sitting In Room 101 (I'm not making this up) at the Grand Hotel, Hartlepool, witnessing the scene. Seasoned political hacks from the Daily Telegraph, the Mirror and a small crowd of colleagues from local and national BBC News leaned forward in their chairs, anxious not to miss a moment. Accusations of ugly racism - however fair or overblown - have become almost routine in this election where the UK Independence Party is concerned. But this was something more. This time, Nigel Farage was doing the accusing.
His target, if you hadn't guessed, was the Scottish National Party. And what he had to say, in my interview for BBC Radio 5 live's Driveprogramme, was guaranteed to provoke an equally ferocious response from the SNP which, I imagine, was the point.
Ukip's rise in the polls appears to have stalled, or slowed at any rate. The near-legendary American pollster, Nate Silver, forecasts Ukip winning a single, solitary parliamentary seat. That may turn out to be a bit conservative, but Farage, who could use a bit more attention, would love to harness more English resentment of the SNP threat and divert attention from the accusations of racism against his party that may, conceivably, be putting off a few potential converts to the Ukip cause.
Farage describes Ukip supporters who don't declare their loyalties to the pollsters as the "shy kippers". Some may be deterred altogether by the fear of being labelled a racist or a xenophobe. Not all though.
I asked the Ukip leader if he wanted those who held racist views to vote for his party. Eventually, and it took a bit of pressing, he said no. When I pointed out a Yougov poll recorded 28% of Ukip supporters admitted to holding "racist opinions", he was understandably keener to rubbish the poll than stand by any assertion that nearly of third of his supporters should vote for some other party.
To be fair, all the other major parties included a surprising proportion of supporters with "racist views". The Liberal Democrats of all people recorded a figure of 12%. And Ukip's pitch concerns more issues than migration.
My own suspicion is that Nigel Farage's theory of the "shy kipper" will turn out to be truer than the big parties would like, and I'm not convinced the Conservatives will be alone in counting the cost of lost support.
I'm writing this as my train from Hartlepool arrives in Edinburgh. I'm on my way to link up briefly with the campaign of the former SNP leader, consummately skilful strategist and political street fighter, Alex Salmond. Can't wait to see how he deals with this latest tirade from Nigel Farage; though even as I write this I can't help feeling Salmond - and his protégé, now boss, Nicola Sturgeon - may just feel they have bigger fish to fry.