Research has found that a drug derived from the substance can thin blood and dissolve blood clots in the brain, saving lives and limiting the damage caused by strokes.

Currently, patients who suffer most types of strokes need to have clot-busting injections within four hours of the attack for the treatment to work.

But studies have found that jabs using a medicine derived from protein in bats' saliva can have the same effect for up to nine hours.

The difference means the drug called Desmoteplase could be given to patients who suffer a stroke while asleep and then wake up hours later.

Vampire bats have been chosen because they use their spit to keep the blood of their prey thin enough to drink.

Doctors at the University Hospital of North Staffordshire are among the first in the UK to test whether vampire bat saliva can save more lives among stroke victims than other treatments.

Consultant Dr Christine Roffe said the NHS trial was in its early stages, but that if it went well, it could be in widespread use within three years. ...