<P> Black Tot Day (31 July 1970) is the name given to the last day on which the Royal Navy issued sailors with a daily rum ration (the daily tot). </P> <P> In the 17th century, the daily drink ration for English sailors was a gallon of beer . Due to the difficulty in storing the large quantities of liquid that this required, in 1655 a half pint of rum was made equivalent and became preferred to beer . Over time, drunkenness on board naval vessels increasingly became a problem and the ration was formalised in naval regulations by Admiral Edward Vernon in 1740 and ordered to be mixed with water in a 4: 1 water to rum ratio and split into two servings per day . </P>

When did the royal navy stop issuing rum