Queen Elizabeth is England's longest reigning monarch, ruling the country for 65 years and counting. There was a time, however, when some people around her apparently plotted to prevent her from taking the throne.

According to Daily Express, the plan to oust Queen Elizabeth, who was then the heir to the throne, was exposed in the documentary Inside Buckingham Palace. Described as a "treasonous plot," some people working with the royal family allegedly had a different replacement in mind when the Queen's father, King George VI, fell ill. 

This happened in 1946, when then-Princess Elizabeth was primed to become the regent as King George VI grew increasingly weak and frail. But, British Intelligent Digest editor Kenneth de Courcy wrote to the king's older brother, the ex-King Edward VIII who was then named the Duke of Windsor, to consider taking over as the regent.

There were apparently concerns that if Princess Elizabeth were to assume her father's role then she will be influenced and surrounded by the Mountbattens or Prince Philip's side of the family. De Courcy told the Duke of Windsor, whom the princess referred to as Uncle David, that the Mountbattens are hungry for power and influence. This could have catastrophic effects to the House of Windsor.

The Duke of Windsor and De Courcy kept with their correspondence with utmost secrecy to avoid being accused of treason. However, he told De Courcy that this matter needed "very careful thought" though there were hints that he wanted to gain back the power that he abdicated for love in 1936. 

A plan was then hatched to potentially declare that Princess Elizabeth is still too young to reign in place of her father. The mood at Buckingham Palace was allegedly filled with paranoia but the old guards were equally appalled at the thought of Prince Philip and the Mountbattens, especially is ambitious Uncle Louis "Dickie" Mountbatten, gaining power over House of Windsor. 

Members of the royal family and the senior royal staff members also warned about the Mountbattens. Prince Philip's cousin said in the documentary that, indeed, many of the old guards felt the Duke of Edinburgh was a dangerous influence on a young Princess Elizabeth.

Princess Elizabeth, however, didn't have to take over as regent when she was still in her early 20s as her father recovered from his illness. Six years later, however, she had to eventually succeed her father after he died of lung cancer. The Duke of Windsor attended his brother's funeral but he was not present when Queen Elizabeth was crowned the Queen of England.