Verbal battles over Damian McBride's memoirs escalated into actual fisticuffs as the publisher of Gordon Brown's ex-spin doctor tussled with a protester from Manchester during a live television interview.
Iain Dale, of Biteback Publishing, ended up scuffling on Brighton seafront with Stuart Holmes to get the veteran campaigner's anti-nuclear banner out of shot.
Sussex police said it was "looking into the circumstances" of the incident outside the Labour Party conference, which took place as Mr McBride talked about his book on ITV's Daybreak.
The barking of Mr Holmes's placard-wearing dog was audible to viewers as - out of shot - a frustrated Mr Dale grabbed the pensioner's rucksack and physically hauled him out of the way.
As they grappled on the pavement, with the dog joining in, their confrontation was filmed by other members of the significant media scrum which has attended Mr McBride's arrival at the conference.
The protester tried to make the best of the situation, holding up his banner reading "No Nukes - Radio Active Dust Cancer Epidemic" to photographers busy recording the scrap.
After a few moments, the pair separated and dusted themselves down, and the protester went back to trying to edge his way into view of the cameras.
Mr Dale said the protester - a familiar face to conference-goers for 30 years - was an "idiot" and said he had only done "what any self-respecting publisher would do" by stepping in.
But Mr Holmes, originally from Manchester and a veteran of three decades of party conferences, said that after speaking to the police he was considering legal action.
Mr Holmes - who was surprised to be told the interview with Mr McBride was being broadcast live - insisted that the ex-spin doctor saw his placard and appeared "happy with it".
"I was not ruining the interview, I was just in the background. I was not saying anything," he said after returning to his familiar pitch outside the entrance to the conference venue.
"Then this giant of a guy turned up and grabbed hold of me. I struggled free and in the process we ended up on the floor."
Mr Holmes, who complained that his hat was also thrown over the railings to the beach, said he would be talking with his lawyers next month but was unlikely to take it further.
"I'm a bit reluctant, I'll think it over," he said, adding that he needed good relations with the media to get his message across about "the potential destruction of the planet" and global health risks posed by nuclear power - and especially the crippled Fukushima nuclear power plant.
"Nobody got injured - well, he might have a few bruises," he added.
Writing on his blog, Mr Dale - also a broadcaster on LBC 97.3 radio - said the only injury was caused by the dog, also named Stuart, apparently biting its owner on the backside during the fracas.
"I knew I shouldn't have had three Weetabix this morning," he joked.
"I did what any self-respecting publisher would do - got out of the car, ran across, got him in an armlock and pulled him out of the shot," he said.
"He started resisting and we ended up in an unseemly tumble on the ground. I was conscious of the photographers and other cameramen who were present filming the whole thing, but I was determined this idiot shouldn't disrupt what was an important interview for my author.
"I am someone who runs a mile from any form of physical confrontation normally, but I never understand why broadcasters seem to accept without question that someone with a placard or a loud voice should disrupt this sort of interview.
"Anyone who has seen the pictures and video can see that there was no real violence. I certainly didn't hurt the guy. He threw a punch at me but missed, and the only injury was when the man's dog bit him on the bum."
He added: "In some ways I have committed the cardinal sin of becoming the story myself, rather than my author, and I regret that. But do I regret that I stepped in to protect my author? No, I do not.
"One of the snappers afterwards said to me that I did what they had all been dying to do for years, as he regularly interferes with their professional work.
"Everyone has an inalienable right to protest, but no one has a right to make a continual nuisance of themselves and interrupt interviews like that."
Mr Holmes said that when he spotted the cameras, he assumed they were for party leader Ed Miliband whom he was keen to confront after being "totally blanked" by him at the TUC conference.