Bangladesh government today declared three-days of state mourning marking the death of Queen Elizabeth II.

The royals of England have spent decades preparing for the queen's demise in order to ensure smooth transition to a new monarch.

President M Abdul Hamid and Prime Minister Sheikh Hasina offered Britain's royal family "heartfelt and deep sympathies" over the death of Queen Elizabeth II.

The British monarchy’s rules state that “a new sovereign succeeds to the throne as soon as his or her predecessor dies.”

The crowning achievement of Britain's Queen Elizabeth, who died on Thursday after 70 years on the throne, was to maintain the popularity of the monarchy across decades of seismic political, social and cultural change that threatened to make it an anachronism.

Prince Charles has been preparing for the crown his entire life. Now, at age 73, that moment has finally arrived.

Queen Elizabeth II was the longest-serving monarch of Great Britain. She has been served by 15 prime ministers, and during her reign, there have been 14 US presidents. Elizabeth remains queen of 15 realms including the United Kingdom, Australia, Canada, New Zealand, Jamaica, Antigua and Barbuda, the Bahamas, Belize, Grenada, Papua New Guinea, Solomon Islands, St Kitts and Nevis, St Lucia, St Vincent and the Grenadines, and Tuvalu. Many countries including India and Pakistan got independence from the British empire during her rule.

Here are some facts about Queen Elizabeth, Britain's longest-reigning monarch.

Queen Elizabeth II, Britain’s longest reigning monarch has passed away at the age of 96, Buckingham Palace said.