Sir: If my experience is anything to go by, John Emsley ('A cup that really cheers', 19 July) is wrong in claiming that withdrawal symptoms after two days without caffeine are a myth. I am a heavy coffee drinker (four big cups a day). It doesn't keep me awake, nor has it yet given me a heart attack, but that may be my good luck. I have plenty of friends who can't drink coffee in the evening.
Once, a friend who is a health enthusiast gave me a pound of decaffeinated and persuaded me to switch to it for a week. I soon had such violent headaches that I had to see my doctor, who at once diagnosed caffeine withdrawal. I reverted to my normal habits and felt fine.