Business is booming at CMC, the London-based financial group, and bankers are pressing to float it. Cruddas, as founder and owner, will have the final say, with the business likely to be valued at between £800m and £900m. If it moves, Cruddas will trade it, apart from sports betting, which he leaves to others. The rest - equities, indices, derivatives, commodities, oil, currencies - are his business. CMC is also an online market-maker, owner of Deal4free.com, a share service for private investors. He also employs bright people who have helped build the software that gives CMC a competitive edge on pricing. In the year to March 2005, CMC made a £40m post-tax profit and is looking to make £48m in the current year. We put a conservative £800m price on the business and add £30m for past salary payments, his Monaco home, and other properties in Britain and France. That makes Cruddas the richest man in the City. Not bad for the son of a Smithfield meat market porter and a cleaner, who grew up in the East End of London.

2. Lord Rothschild and Family £480m
age 69, RIT Capital

Lord Rothschild split from the NM Rothschild bank in 1980 and took over RIT Capital, a small investment trust. RIT has grown to a £1.1 billion operation, and Rothschild and his family have almost a quarter of the shares, worth £295m after a strong performance in 2004-05. In 1989 Rothschild inherited £93m from an aunt. We add £120m for other assets including his art, a small farm and nursery operation, and sale proceeds from various Rothschild investments that have come good over the years (such as £40m made from selling the free ad paper Loot in 2000). In all Rothschild and his immediate branch of the family are worth £480m.

3. Louis Bacon £425m

Moore Europe Capital, the London arm of hedge fund group, Moore Capital, is doing pretty well. In 2003, it made £15.4m profit on £110.7m sales. Yet it is but a small part of Wall Street-based Moore Capital, which has over $9 billion in funds under management, making it one of the top investment groups in the world. It plays the currency, share and commodity markets with enormous success under its American chairman and chief executive, Louis Bacon. He finds London the most convenient location and through his huge profits, has been one of Wall Street's highest earners making $100m a year. Forbes put him at £375m in its list of the 400 richest Americans in October 2004. We put Bacon at £425m.

4. Michael Spencer £382m
age 50, Icap

Daily trades on Icap's electronic broking platforms exceeded 500 billion for the first time in February. Good news indeed for Michael Spencer, Icap's founder who topped our list last year and is now one of the legends in the City. Today ICAP is the world's biggest money broker, and Spencer has a £282m stake. Other stakes such as £17m in Numis, the quoted broker, and a £36m stake in City Index, the spread betting operation plus the sale of his stake in another betting operation, Blue Square for £27m, add a further £81m. With past salaries and dividends, Spencer is easily worth £372m after-tax.

5. John Duffield £327m
age 65, New Star

Retirement does not beckon for 65-year-old Duffield. 'I've decided I'm not going to retire until I'm 90,' he said recently. But he could certainly afford to retire. His New Star Asset Management group, started in 2001, had been groomed for a flotation in September 2004 but that was postponed due to stock market conditions. It is now planned for later this year. The price could be as much as £600m, valuing Duffield's 20% stake at £120m. Duffield is the star fund manager who famously started the Jupiter Tyndall investment operation in 1986 with a desk and a secretary. Nine years later he sold the business to the German bank Commerzbank in a complex earn-out deal from which he made around £185m. Duffield also has a £43m stake in the separate and quoted New Star Investment Trust plus £1.2m net assets in his Marcham Farms operation. But allowing for tax, we value Duffield at £327m.

6. Sir Ronnie Cohen £260m
age 59, Apax Partners

A former Liberal parliamentary candidate, Sir Ronnie Cohen was an early convert to New Labour and a financial backer of the party.

Arriving from Egpyt after Suez as a near penniless 12-year-old refugee who could speak only a few words of English, Cohen has risen to become the senior figure in the British private-equity industry.

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