Danny Truell recently urged charities to take more risks with their investments. He practised what he preached yesterday as the Wellcome Trust, Britain's largest charity, disclosed that it had taken an estimated £100 million stake in Marks & Spencer.

Only a month ago M&S issued a profit warning that wiped £1.2 billion from its market value. Traders said yesterday that the trust's decision to buy into the under-fire retailer suggested that shares in M&S have fallen so far that they may now offer good value.

Value has been central to Mr Truell's career. Before joining the Wellcome Trust as its chief investment officer three years ago, he was the high-flying managing director of Goldman Sachs Asset Management.

Today he presides over a £15 billion charitable fund, the second-largest in the world, making investments to generate the money that Wellcome uses to finance biomedical research.

Asked why he had left Goldman Sachs to join a charity, his reply was simple: “This is one of the best jobs one could have in the investment world.”

Under Mr Truell, 44, the Wellcome Trust has adopted more modern investment practices and become as influential on the world stage as the charitable funds run by Harvard and Yale.

The trust's exposure to equities has fallen to 55 per cent of the portfolio under Mr Truell, and two years ago it became the first UK charity to issue a bond that was linked to general investment, rather than to any one structural project.

Investment returns were 17 per cent last year, in line with the double-digit returns the portfolio has made every year since 1936, when it was set up with a £2 million bequest - £72 million in today's money - from Sir Henry Wellcome. The fund swelled in 1986 when it realised £7.6 billion from its investment in Wellcome plc, which became GlaxoSmithKline.

It has become such a big operation that last year it teamed with Terra Firma, the private equity fund run by Guy Hands, to put together an abortive £10 billion takeover bid for Alliance Boots.

Mr Truell is on the board of the Pension Corporation, the pension management specialist set up by his brother Edmund. The two also run the Truell Charitable Foundation.

Edmund says: “Both he and I are good at making money. So we thought, what's the best way of organising our charitable instincts?”

M&S shareholders will hope that Danny Truell is on to another winner.