Thousands of Britons who suffer from chronic migraines could benefit from a drug found to relieve previously untreatable headache pain.

Nine in ten patients with debilitating migraines reported immediate pain relief after receiving an infusion of a local anaesthetic called lidocaine. Researchers believe that it could “break the cycle of pain” experienced by sufferers.

There is no cure for migraines, which affect six million people in Britain, although patients may be prescribed painkillers or Botox injections to ease symptoms. Migraines are the second leading cause of work absence, costing the economy £2.25 billion a year.

About one in 1,000 people suffer chronic migraines, meaning they get headaches at least 15 days a month. The new study said lidocaine appeared to be suitable for such patients,