So what? Who he? Knight is head of strategy at the London office of Nomura Research Institute, the world's biggest stockbroker, and his latest pronouncement sent the stock market down 16 points on Thursday morning, before it was revived by the Bundesbank cutting German interest rates.
The tall, bespectacled Knight is the first leading strategist to cut his forecast after months of upgrading by UK strategists, thus maintaining his record of keeping ahead of the herd.
But Thursday's market fall was no more than a routine nod, compared with Knight's coup on 16 September, 1992. On that morning he told clients to buy as many UK shares as they could. Before nightfall John Major had taken Britain out of the European Exchange Rate Mechanism. The London market rocketed.
People who can do that are worth many thousands of pounds in commission to their employers as orders flow in from grateful fund managers.
That is the theory, at any rate. But David Manning, director of UK equities at Legal & General Group, said: 'We cannot run pounds 30bn of assets on the basis of Knight's change of mind from week to week. Nevertheless, his call on Japan last year was excellent, and he does make you sit and think.' Knight declared last June that the Tokyo stock market rally was over, a view that reportedly earned Nomura's head of research in Tokyo a carpeting at the Japanese Ministry of Finance.
Unbowed, Knight then recommended in October that investors move out of the US and Japan and into other Asian stock markets, catching the surge in the shares of emerging countries.
By early last month he was calling those markets overheated, arguing that it was time to move money back into Tokyo. In the next three days, the Hong Kong market plunged by a tenth while Tokyo rose 4 per cent.
Asked whether or not Knight's outpourings had encouraged L&G to put more business Nomura's way, Manning said: 'He certainly keeps Nomura in our dealers' minds - but we couldn't look back and say how much of the commission we have paid them was down to him alone.'
In practice he earns the six-figure salary that Nomura pays him, by jetting around the world for a third of the year, giving talks and presentations. Fund managers appreciate the value of these sessions, thanks to Knight's ability to challenge conventional wisdom and get debates going. But the information flows in both directions: while he is playing the audience, his eyes are skinned for their reaction.
'Everyone thinks I'm just a non-stop talker,' he explained, 'but I spend most of the time listening and looking for signs in their body language: whether eyebrows are raised, whether smiles are forced or natural. Even the way they wince can tell you if the guy has bought the story, is about to buy the story, or has already sold the stock.'
As soon as he gets back to his office or hotel room, Knight faxes these impressions back to Nomura so the dealers can adjust their views of the market.
In between personal appearances Knight publishes views on the economies and stock markets of any countries that catch his eye, whenever the spirit moves him.
'I have really abandoned fixed schedules for document production,' he sniffs.
'It may mean that I write three pieces in a week, or nothing for six weeks, but I can't write to order. I am amazed at all these people who have good ideas on Thursday, simply because it's Thursday.'
Knight's good idea last Thursday was that, 'as trivial as it must seem to the outside world, the Chancellor's decision to shave a quarter-point off UK base rates rang the bell for the 'top' in economic optimism . . . and, more worryingly, the speed of decay from 'peak' levels could be quite rapid.' That was promptly rubbished by other market observers, but the merits of the argument were beside the point: what mattered was that enough people took it seriously.
Although Knight was rated second for UK equity market forecasting last year by the journal Institutional Investor, it is some years since he has been ranked in the top three in the annual Extel survey of City fund managers. Nevertheless, what he might lack in kudos he makes up for in showmanship.
Despite his claims to be a listener, Knight is a non-stop talker - reluctant to give a one-word answer to a question when a thousand words would do. The roots of his fervour lie in the competitive household in which Knight was brought up, near Epping Forest in Essex.
Knight, the youngest of three brothers, is regarded as the slowcoach of a family led by a father who was a director of the Ever Ready batteries group and whose late mother ran a ceiling tiles business. The eldest brother, Chris, is a physicist and the other, Tim, is a zoologist. 'I am completely looked down upon,' Knight lamented.
Nick, Chris and Tim endured a miserable year in 1981, when their mother died. In the same year, Ever Ready was taken over by Hanson after a bitter battle.
But their father bought out his research and technology division, selling it a few years later to Dowty at a handsome profit.
After Davenant Foundation grammar school, Nick had the choice of following one brother to Queens' College, Cambridge, or the other to The Queen's College, Oxford. He opted for Cambridge, where he captained the university badminton team and got a 2:1 degree in economics.
He became a trainee at Hambros Bank, but was still languishing in Hambros's back office in Brentwood, Essex, when in 1983 he moved to the stockbroking firm James Capel.
That was where Knight made what he acknowledges was his biggest forecasting blunder - recommending his followers buy into the London stock market in September 1987, only weeks before the October market crash.
'Of course forecasts go wrong,' Knight shrugged. 'That is part and parcel of the business. Even George Soros doesn't get them all right. But the 1987 prediction has left scars: the madness of the crowd took one in at the top. Never again.'
Despite that humbling episode, Knight's progress was swift. He left Capel five years later as head of strategy, to be managing director of research at the ill-fated US house of Drexel Burnham Lambert. Within a year he was snapped up by Nomura.
But he denies he has any magic formula for divining market trends. 'As an economist, I try to follow the economic cycle and where it's going,' he said. 'But as a strategist, I am aware that the market is a mechanism for discounting trends. People forget the extent to which it does that. I am not a believer in black boxes full of equations.'
If that sounds like a plea for educated gut feelings it would not be far wrong, for Knight makes no secret of the degree to which he feeds back to the market what he hears from the market.
Although he refuses to be bound by a weekly schedule, Knight has the priceless facility of being able to write quickly in almost any surroundings.
When the mood takes him, he delights in writing his research circulars on a notebook computer as he commutes into the City on the 6.10 train from Saffron Walden. 'Without the distraction of the phone,' he says, 'I can fill an A4 page by the time I arrive at Liverpool Street at 7.06.'
Knight is sufficiently bound up in his work to deny having any hobbies, other than his family. He takes his wife, Sally, a teacher, and young children, Peter and Emma, to a farmhouse in Brittany.
'The last thing I want is to get on another plane to go on holiday,' he said. 'And buying property is a way for me to put money back into the family.'
So, no, the stock market's best- known pundit apparently does not have a vast portfolio of stocks and shares salted away. However, he would like the opportunity to show that he can actually manage money instead of just telling others how to do it.
''I have no wish to climb the management ladder at Nomura,' Knight said, 'but I wouldn't mind turning my hand to fund management one of these days. After all, there's nothing like pounds, shillings and pence, is there?'
Meanwhile, traders in the London stock market will be relieved to know that the garrulous guru is striving might and main to maintain a decent silence - for the time being.
'Quite honestly, if we did not have to make any more changes for a while, we'd be quite happy,' he declared.
A view that many of his exhausted disciples will applaud.