In common with so many problems involving young men in modern London, it was a squall about reputation and respect

After a lifetime at the helm of the world's most powerful media organisation and in the crosshairs of the left, Rupert Murdoch has, of necessity, developed a reasonably thick skin.

The Dirty Digger is how he is disrespectfully referred to by Private Eye. Spitting Image always portrayed him as a shouty figure, irredeemably uncouth.

But his son James seems less ready to turn the other cheek, as it were. And this would seem to be the most plausible explanation for why Murdoch the younger, the chairman and chief executive News Corporation Europe and Asia, caused a media sensation on Wednesday by striding across the editorial floor at the Independent newspaper to berate its editor-in-chief, Simon Kelner.

In common with so many of the unpleasant episodes involving angry young men in modern London, it was a squall about reputation and respect. The newly relaunched Independent had produced a series of relatively innocuous promotional ads assuring readers: "Rupert Murdoch won't decide this election. You will."

There is no evidence that Murdoch senior has even seen the ads, but witnesses report that directly upon seeing Kelner, who was supervising the final production stages of that night's paper, Murdoch the younger began angry remonstrations. "What are you fucking playing at?" was his opening gambit.

A bewildered Kelner quickly ushered his visitors into his office, where they remained for what have been described as "frank and full discussions" for another 20 minutes. All were grim-faced as Murdoch, carrying a promotional copy of the Independent, accused the rival editor of breaking the unwritten code that proprietors do not attack each other and of besmirching his father's reputation. With his piece said and with the matter unresolved, the aggrieved media mogul left.

The episode left experienced journalists shocked. "They strode in like a scene out of Dodge City," said one. "Murdoch scanned the room, you could almost hear him saying 'Where is he?'"

Another likened the arrival in the newsroom of Murdoch and Rebekah Brooks, the chief executive of News International, to a mafia visit. "It was so bizarre. He came in all menace. You know the sort of thing: 'The boss has heard what you have been saying about him. He doesn't like it.'"

There was indeed a family style closing of ranks today, as both News International and the Independent declined to comment. But then, on one level, what occurred had elements of a family squabble.

Earlier that day, Brooks had telephoned Kelner to raise concerns about the personalised ad. It appears to have been a relatively cordial conversation. The two have in the past socialised as part of a high-powered media set centred in Oxfordshire. Blenheim is the Murdoch family retreat and it is said that Kelner has spent time "chatting to Rupert" while staying in the area as Brooks's guest.

He will have been unprepared for a such an attack from Murdoch junior, another familiar face in Oxfordshire, but then the outburst took everyone by surprise. Brooks and Murdoch actually travelled to Kensington to see Lord Rothermere at Associated Newspapers, publishers of the Daily Mail and the proprietor's group managing director, Kevin Beatty. Associated say they discussed commercial matters such digital and electronic media and iPads.

It is acknowledged that Murdoch has been meeting other heavyweight figures in the media industry to forward his father's belief that newspaper websites should be shielded from free use by a revenue-raising paywall. The Times and Sunday Times will erect a paywall in June.

The Daily Mail has set its face against the idea, but still Murdoch and Brooks appeared to be in good spirits when they ended their meeting with Rothermere and Beatty on the sixth floor, merely asking for directions to the Independent office on the second. Even then there was no immediate sign of trouble. Brooks's first comment to Kelner was "Surprise – look who's here to see you!"

There are, of course, reasons why Murdoch junior might be particularly cranky right now. The paywall experiment is an acknowledged gamble which other British outlets seem reluctant to take. And there is unease that despite the full blooded, war-footing support of the Sun, David Cameron's Conservatives are failing to establish the sort of lead that was expected of them.

Blogging today, Murdoch's biographer Michael Wolff said jitters among the two lieutenants are inevitable because Brooks persuaded James Murdoch to throw the company's weight behind Cameron's Conservatives and the young Murdoch persuaded his father. The magnate does not like bad advice, says Woolf. "Murdoch likes winners, even more than he likes Conservatives."

The fallout continued elsewhere today, as Associated complained bitterly about a Channel 4 blogpost suggesting that James Murdoch may have had a political motive for his visit the Mail – to construct a joint strategy to counteract the rise of the Liberal Democrats. Absolute rubbish, say Associated.

Repercussions for the Independent, too, which engaged the publicist Matthew Freud to work on its relaunch, only to find that the unsolicited actions of his brother-in-law James Murdoch have done the job just as effectively.

Practical repercussions as well. This afternoon, for the first time since the paper moved to Kensington 11 months ago, the newsroom door was secured with a swipe-card lock.