His probably doomed broadsheet, all-business newspaper had one of the rockiest launches in Fleet Street history, and Rubython is convinced guerrilla tactics by competitors had much to with the difficult debut.
"Sure, it was intentional. They set out to kill us off, and they seem to think they have now seen off the threat," Rubython said over the weekend, his voice showing the strains of a month of turmoil and stress. Asked how he was holding up, he conceded that "it is very difficult to put out a newspaper under these circumstances".
What circumstances? "Having absolutely no money at all."
The dream of Sunday Business has dominated Rubython's thoughts for two years, ever since he bowed out of his last, equally controversial project, the writ-dogged Business Age, which he and partners sold to the Dutch publisher VNU for a reported pounds 3m.
In the few months before the launch of Sunday Business in mid-April, Rubython worked furiously to raise the pounds 10m he needed. The City was not interested, and a planned float failed to get off the ground. Would-be investors were wooed with an impressive business plan and an authoritative marketing study. But one by one, they backed out, leaving Rubython and a few friends high and dry.
Only an emergency lifeline offered on "impulse" by Owen Oyston, the millionaire socialist, allowed the launch to proceed at all. Damagingly, the cash was enough - barely - to get the paper printed and distributed, but all promotion plans were abandoned and some staff had to wait for their wages.
Against the odds, the first issue hit the streets on 21 April, thick and studded with stories. Some of these were billed as "scoops" - although one or two had been in other media months before, and others were immediately denied by the companies involved. Still, the first issue sold a respectable 145,000 - close to the 150,000 level Rubython hoped to reach once the newspaper's niche in the marketplace was secure.
But without a promotional campaign to entice would-be readers, and without some positive word of mouth, that level of sales was impossible to maintain. By this past Sunday, sales were down to perhaps 60,000 and advertising had visibly collapsed, with page after page of the main broadsheet section bereft of adverts. That left some concluding that there is no real market for an all-business weekend newspaper, however hard one tries.
Rubython is oddly sanguine about all this, and insists the newspaper is not yet dead. He says a series of meetings with potential investors is planned for this week, with a key meeting to come tomorrow. When asked whether the paper will come out again this week, you can almost hear the shrug in his voice: "I really can't say."
He is far from sanguine about the "campaign" waged against him, however. He claims the Telegraph led industry efforts to close him down, by putting pressure on advertisers, printers and even his ad agency.
The Telegraph jointly owns, with United News & Media, the West Ferry printworks in Docklands, which had contracted to print Sunday Business. A few days before the launch, West Ferry cancelled the contract, over concerns that Rubython would not be able to pay. The advertising agency ARC dropped the Sunday Business account for similar reasons.
Both ARC and West Ferry insist there was no conspiracy, but Rubython doesn't buy it. "No printer pulls out like that. They are happy to do the work as long as they are paid in advance. West Ferry did not even wait to see whether we would be able to pay. No independent publisher is ever going to go to West Ferry again."
Rubython didn't much like the coverage of his launch in other Fleet Street newspapers, some of which gleefully reported the birth pains in diary items and the odd, bitchy story. "I guess I should have expected it, but it took me by surprise."
He says he had not reckoned on the Telegraph's response to the newspaper's launch. "I guess as number two in the Sunday market they felt threatened. We thought they were going to be friends, since we were targeting the market leader, the Sunday Times."
Rubython is so sure the competition mounted a formal campaign that he is amazingly reckless with charges. And the accusations do not end with the turmoil over the Sunday Business launch. He hints that he has "terrific" information on several media executives, which he intends to publish.
Some of it he even shared, on the record, with the Independent. But he knows, with his journalism background, that none of it is going to be repeated here. The charges are levelled with that mixture of charm and recklessless that is the very essence of Rubython's personality.
It is a mixture that one usually associates with far more important people: senior newspaper executives, for example, or the top man at some of the country's large broadcasters. They, too, often strike one as eccentric, arbitrary, reckless, churlish, impish and not a little charming.
Not yet a media mogul, Rubython's personality and instincts have led him into trouble in the past. Business Age was sued time and time again over highly speculative stories. Most famously, a Business Age journalist suggested that Kelvin MacKenzie, now the head of Mirror Television, had been sacked from his job at Rupert Murdoch's pay-TV company, BSkyB. MacKenzie launched a suit, which Rubython was left to defend alone following the sale of Business Age to VNU. The Dutch had quite sensibly arranged to buy the title without the backlog of legal troubles. The case was settled out of court earlier this year, with Rubython apologising.
Sunday Business itself has been out for a month, and has yet to attract a formal legal action. But neither has it really had any great stories - agenda-setting exposes that the rest of Fleet Street has to follow. Many who have worked with him say Rubython is a "real" journalist. He loves the story, and he revels in the chase. At Business Age, he was so hands-on that virtually every story bore his mark. Money problems at Sunday Business mean that he hasn't had time to run the whole show: he is too busy talking to would-be investors.
As a result, the product looks a bit busy and brash, but doesn't have "bottom" (nor, as of this past weekend, does it have a colour supplement: the most obvious casualty of the cash crisis).
Rubython concedes that the current situation is untenable. No paper can survive week to week with no promotional budget and with an increasingly nervous staff. "Long-term financing will have to be found, that's obvious," he says.
Meanwhile, the staff has divided into two camps. Some - the younger, enthusiastic ones - seem to thrive on a steady diet of crisis. Others are looking frantically for the exit. And Rubython? He's still looking for money.