Lovers of dark chocolate have known for some time that their favourite treat can help protect them against high blood pressure and cut the risk of diabetes.

But now scientists say that it can even benefit those who are already at high risk of heart attacks and strokes.

Although regular chocolate eating doesn't work quite as well as drugs, the researchers say it has virtually no side effects and, perhaps not surprisingly 'high rates of compliance'.

A team of researchers from universities in Melbourne, Australia, used a mathematical model to predict the effects and cost effectiveness of daily dark chocolate consumption in 2,013 individuals at high risk of heart disease over a decade.

They all had metabolic syndrome a mix of problems including raised blood pressure, obesity, high fat levels in the blood and an inability to control blood sugar levels but no history of heart disease or diabetes and they were not on blood pressure drugs.

Daily consumption of 100g of dark chocolate could potentially avert 70 non-fatal and 15 fatal cardiovascular events per 10,000 people treated over ten years, according to the study published on bmj.com.

This could be considered an effective intervention, said the researchers. It would be cost-effective too, costing £25 a year per head of population.

The protective effects have been shown only for dark chocolate which is at least 60-70 per cent cocoa. Milk or white chocolate does not provide the same benefits.

It is rich in flavonoids which are known to have heart protecting effects. Sceptics say the high calorie content of chocolate tends to offset the benefits.

Previous research shows eating chocolate reduces blood pressure and improves insulin sensitivity, reducing the risk of diabetes.