During the reign of Queen Elizabeth I, being a Catholic was illegal and those suspected of practicing Catholicism were charged with treason against England. Elizabeth I was the cousin of Mary Queen of Scots, and after Mary Queen of Scots was forcibly removed from her kingdom, she was brought in by Elizabeth I despite their difference in religion. Mary Queen of Scots was a devout Catholic and Elizabeth I was a practicing Protestant. Eventually, rumors circulated that Mary Queen of Scots would try to usurp the throne from her cousin. Clandestine messages were sent inside the heels of shoes, within the personal private areas of servants, within the pages of books, and using many other inventive solutions. The most effective way of sending secret messages during this period, was inside the cork of beer barrels as none of Elizabeth I guards ever thought to look there. Lemon juice was used as invisible ink which when heated with a candle flame, revealed clear messages and enabled Mary Queen of Scots and her allies to conspire against Elizabeth I. Mary Queen of Scots was eventually entrapped and convicted with her co-conspirators being publicly hung nearly until death, then brought down and disemboweled and shown their bowels, after which their limbs were cut off and displayed in prominent parts of London, England. Mary Queen of Scots was stayed of her execution as Elizabeth I would not sign her death warrant. It is estimated that this period is when British intelligence, specifically MI5 and MI6, began to formulate. The abbreviation “MI” stands for “military intelligence” and each number stands for “section 5” and “section 6”