How much caffeine? (per cup)

Filter coffee - 80-115 mg Instant coffee - 65 mg Black tea - 40-60 mg Cocoa - 4 mg Can of cola - 35-60 mg

In all, 58% of headache sufferers said that taking caffeine capsules was completely successful, the same proportion as in those taking ibruprofen only - and many said they felt better more swiftly.

Tension headaches involve constant, dull pain, although not generally as excrutiating as a migraine.

Just as good

Pain is often accompanied by muscle tightness in the shoulders and neck - and can last for days.

The Diamond team found that when caffeine was added to standard painkillers, 70% of patients reported complete relief, as opposed to 58%.

On average, Britons are still said to consume 3.5 cups of tea a day.

Some studies have suggested that other chemicals in the drink may have health benefits.

However, the overall health benefits of caffeine are less clear-cut.

Some studies have linked high caffeine consumption with an increased number of headaches.

Caffeine can cause, in higher doses, a temporary rise in blood pressure, and some doctors suggest that people with heart rhythm problems should avoid it.