They may be the closest thing Britain has to Bill and Melinda Gates, with charitable funds worth over £1 billion to give away. But you won’t find Chris Hohn and his wife, Jamie Cooper-Hohn, on the pages of the colour supplements and that is just how they want things to stay.

Ms Cooper-Hohn runs the Children’s Investment Fund Foundation (Ciff), which she co-founded with her husband, the manager of TCI, the hedge fund. But the couple are so publicity-shy that they insist no photographs are taken.

Ms Cooper-Hohn says there are good reasons for her low profile, in particular, the highly unusual way in which Ciff operates. Unlike almost every other foundation, it does not pick causes and then fund projects doing good work in that field. Instead it sets sweeping goals — reducing childhood pneumonia by 20 per cent, for example — then works out how to do it.

Governments or UN programmes may work this way but foundations do not, so it is uncharted territory. Ms Cooper-Hohn admits mistakes have been made in Ciff’s short life. “I passionately believe in our approach, but it is new and even in the last few years we have learnt so much and re-engineered our own approach. I don’t need to get out there and claim I have the answers. We have not earned the right to promote our model or myself.”

The couple also have four young children and do not want them in the limelight. “The other thing is, if we are going to get this right and really affect the way philanthropy is done, it has to be about Ciff. It can’t be about Chris and Jamie. That is a distraction.”

The foundation was set up in 2002 as a vehicle through which Mr Hohn could give away his annual bonus and, according to his wife, give him a reason to “get out of bed in the morning”.

Shortly afterwards, they devised the plan to link the foundation to the returns from Mr Hohn’s new hedge fund. It concentrates its work on childhood survival, education and nutrition, mostly in Africa and Asia.

Ms Cooper-Hohn believes that Ciff’s approach should be used by more foundations. Too many, she says, fail to define what they mean by success.

“Yes, we are different. Virtually all foundations fund activities. If they want to work on childhood pneumonia, they find projects working on respiratory illnesses. We say we will fund a 20 per cent reduction in morbidity, and we will model how to get there. If the evidence shows sleeping under a blanket cuts morbidity by 3 per cent, and health workers making the right call between malaria and pneumonia is 12 per cent, the programme builds from there. And we prioritise the 12 per cent. All activities are not equal and you need to know to get the big win. If it is training community health workers to distinguish between malaria and pneumonia, we will retrain huge cadres and fund that upfront.”

But her practical approach means knowing when it is time to end projects that are not working or cost too much. This has happened twice in the past six months alone. A programme on Aids in Uganda was pulled when the infection rate was found to be 4 instead of 9 per cent during door-to-door testing. The lower infection rates showed other programmes were successfully reaching the households targeted by Ciff.

More difficult was a decision to pull out of a literacy programme in an Indian province that uses a new teaching method with a proven higher success rate than other methods.

But there have been enormous hits, one of the most acclaimed being a bulk-buy of drugs that prevent mothers from passing HIV to their children. At $1,500 (£900) per child per year, they had been seen as prohibitively expensive. Ciff joined with the Clinton Foundation and opened talks directly with the drug manufacturers and got the price reduced to $180. The success of the programme attracted a consortium led by the French Government to expand it and forge a further cut in the cost to just $50 per child annually.

Times Recommends

• ‘Lame duck’ fear for FSA as chief quits
• Storm over bailout of EU's most ailing economy
• Northern Rock to drop 100% savings guarantee