Will anyone dare challenge the City's super rich hedgies?

But all the signs point to a new target looming in the sights of MPs, unions and pressure groups. Compared with hedge fund managers, the private equity players look like amateurs.

The leading "hedgies" as they are known, are richer, if anything even more secretive and often domiciled overseas so to keep tax liability to a minimum. Unlike private equity, they don't own and run the businesses they invest in.

Run out of small offices, predominantly based in Mayfair and St James's, they are entirely unregulated and interested only in taking positions in a company, commodity or currency and making a quick turn.

Increasingly they are able to determine the direction of companies, even the very best-known in the world, with tens of thousands of employees and investors to devastating effect. ABN Amro decided to sell to Barclays after a hedge fund, The Children's Investment Fund, queried its strategy. How much did this fund own of ABN Amro? Just one per cent.

Similarly, Cadbury Schweppes took the momentous decision to break itself into two, offloading its US soft drinks business, after Trian Fund Management, controlled by US investor Nelson Peltz, appeared on its share register.

Peltz bought a mere three per cent but it was enough to send the venerable confectionery and drinks combine into an almighty tizz.

Moody's, the respected rating agency, reports that "activist" hedge funds are bad for the businesses they target. It says they demand companies return cash to shareholders, are broken up or sold to private equity. Mark Watson, one of the study's authors, says: "It is almost universally bad for credit quality." A report by the Organisation for Economic Co-operation and Development last month said there are 120 "activist" funds worldwide with $50 billion at their disposal. That buys them an awful lot of bargaining power.

Hedge funds' only duty is to the people who invest in them. Whereas private equity can point to pension funds and other public foundations and institutions as accounting for the lion's share of their assets, hedge funds cannot. Their investors predominantly are rich people who want to get richer. These "high net worth individuals", as the industry likes to call them, typically invest $1 million to $20 million in a fund.

Another piece of analysis, from Greenwich Associates, the financial services consultancy, found that only 25 per cent of the money pumped into hedge funds comes from pension schemes and similar, publicly-operated bodies.

Once the tax argument is resolved, the attack on private equity will most likely end and a new line of inquiry will open up. Already, there are stirrings. The identical campaigners that provoked the backlash against private equity are making similar, angry claims about hedge funds. The GMB union has sent its members a bulletin, highlighting a report by the European Parliament Socialist Group that "throws the spotlight on secretive hedge funds and private equity deals, raising concerns over their impact on EU job creation policy".

Hedge funds are in a much more vulnerable position than private equity.

The hedge fund operators really are "casino capitalists". It's impossible for them to argue they have the long-term interests of a company and its many employees at heart. They can't point to a business and say "we invested in that, we turned it round, we created 2,000 extra jobs".

The hedge funds can see what is coming.

Thirteen controllers of the biggest funds have banded together under the chairmanship of Sir Andrew Large, former deputy governor of the Bank of England, to fight their corner. Eleven are from London, one from the US and one from Sweden. The 11 from London are together worth more than £1.5 billion.

Here, we publish the 20 richest hedge fund operators we have been able to identify in London. They don't include Chris Hohn, founder of The Children's Investment Fund, for the simple reason that he has given away the bulk of what he earns (his generosity is in marked contrast to the aggression sometimes displayed by his fund). Last year, he donated £230 million to charity, making him one of the country's most generous philanthropists.

His wife Jamie runs the foundation, which receives the cash from the fund now more than $1 billion.

Hohn is the exception. While other hedge fund operators also support good causes, they are not in his league. Their main motivation is making money for themselves and their unknown clients..