A safe oral contraceptive for men has eluded scientists but now technology may provide an alternative.

Bill Gates is the tech nerd who pioneered home computers, built up a $600 billion software firm on the back of this and was named the world’s richest man for 16 years.

The Microsoft founder is no slouch when it comes to philanthropy either. The Bill & Melinda Gates Foundation, which he founded with his wife in 1994, has cut polio cases by 99 per cent worldwide and revitalised the international push for scientific solutions to global health problems.

One of these solutions is better access to contraception for the 220 million women in developing countries lacking the information and the means to control their fertility. It is a long-term goal of the foundation to reduce the annual 90 million unintended pregnancies and 50 million abortions worldwide.

In 2012, the foundation set the ambitious aim of providing contraception for 120 million more women and girls by 2020, but now the target is slipping from reach.

To keep the hope alive, the organisation is upping its contribution to the project by a quarter, providing an extra £95 million — and some of that money is being invested in creating a safe and effective male contraceptive pill.

This is a challenge that, for decades, has confounded some of the best scientific minds in the world.

So far, their efforts have come to nothing, because where contraception is concerned, Mother Nature stubbornly thumbs her nose at sexual equality.

While women have access to a range of contraceptives  — men still have only one safe method: the condom, which has been around since the mid-17th century.

So a gap in the market exists, and that’s where the male pill comes in.

But will Gates’s money — £730,000 of which will go initially to the University of Dundee — and all the other vast funds committed to the pursuit of this Holy Grail of contraception ever deliver?

One thing is for certain: it’s going to take an awful lot of faith. Not only faith in science — but faith in men, too. For even if scientists are successful, critics argue, it will never be practicable.

The solution, if it does arrive, maybe technological, rather than pharmaceutical. Incredible as this sounds, it could involve a switch implanted in the body to turn sperm ducts on and off.

Stopping men producing viable sperm might sound simple when set against miracles of modern medicine such as heart-lung transplants, stem-cell therapies and test-tube babies.

However, it is very difficult indeed to achieve.

Shutting down the male reproductive system without causing damaging effects on bodies and brains has so far proved impossible.

One of the most promising recent possibilities is a drug that combines a synthetic version of the male hormone testosterone with progestin — a hormone involved in pregnancy and used in birth-control pills for women.

In tests, the combination was found to inhibit sperm production in male lab animals. But in 2016, a World Health Organisation trial involving men had to be halted prematurely — despite success in making men temporarily infertile — because of yet more worrying side-effects.

Nearly a fifth of those taking part reported emotional problems, such as depression. Others suffered muscle pain and skin disorders. Yet the volunteers were reluctant to stop taking the drug because, due to the synthetic testosterone, it had intensified their sex-drives.

Meanwhile, scientists are still trying to develop a new formula. The U.S. National Institutes of Health’s Contraceptive Development Programme is about to trial a gel containing testosterone and progesterone that is rubbed regularly into men’s backs and shoulders.

The hope is that, by delivering the drug through the skin, it will have a slower release into the body and might not trigger side-effects.

Other scientists are trying to create a male pill from a lethal poison used by African hunters. Ouabain is a toxic extract from African plants that rapidly causes cardiac arrest — but it can also inhibit the mobility of human sperm.

It takes about 12 years to take a new drug to market. On the way, 90 per cent fail safety and effectiveness tests. Meanwhile, the world is moving away from hormonal contraceptive pills.

Professor Sujoy Guha, a biomedical engineer at the Indian Institute of Technology, has pioneered a system that involves injecting a chemical gel into the vas deferens to block sperm, rather than cutting or tying the tubes.

The vasectomy can be reversed with an injection that breaks down the gel.

Professor Guha claims that his trials have succeeded in about 540 Indian men for up to 13 years, and that the method will be widely available within the next two years.

Meanwhile, in Germany, Clemens Bimek, a professor of urology, has developed an electronic valve that can be implanted in sperm ducts and opened and closed with a switch less than 2cm long.

Implanted in the testes, it involves a 30-minute procedure under local anaesthetic.

Such an invention would have sounded outlandish a decade ago but it is now in sync with a technology-obsessed world where men (and women) want to keep chemicals out of their bodies — and keep their options open when it comes to their own fertility.