Prince Philip has been at the Queen's side throughout her reign, offering her advice and support in best and worst moments.
When they tied the knot, she was Princess Elizabeth and the couple got to enjoy a lot of freedom as a young and in love royal couple.
But when George VI died suddenly in February 1952, she became Queen at the age of just 25.
As she took on the huge responsibilities that come with sitting on the throne, life also changed forever for her husband.
On their wedding day he gave up his Greek and Danish titles to become the Duke of Edinburgh, but he would never be allowed the title of King.
The reason for this is that according to the old patriarchal system, Kings outrank Queens, which would mean he would technically be higher than the Queen - which isn't allowed as he married into the royal family rather than being born into it.
On February 22, 1957 the Palace issued a statement which read: “The Queen has been pleased by Letters Patent under the Great Seal of the Realm bearing date 22nd February, 1957, to give and grant unto His Royal Highness the Duke of Edinburgh, K.G., K.T., G.B.E., the style and titular dignity of a Prince of the United Kingdom of Great Britain and Northern Ireland, Whitehall.
“The Queen has been pleased to declare her will and pleasure that His 'Royal Highness the Duke of Edinburgh shall henceforth be known as His Royal Highness The Prince Philip, Duke of Edinburgh.”
However, the rules mean it will be a different story when Prince William becomes King one day with Kate by his side.
It's likely that the Duchess of Cambridge will become Queen Consort, and it's likely that she will opt to be Queen Catherine.
Like Philip, as she wasn't born into the royal family she can never be Queen in her own right but she can take the 'Consort' role - which is what many wives have done in the past.
King George VI's wife became Queen Elizabeth, before becoming better known as The Queen Mother after the King's death.
King George V's wife was Queen Mary.
Explaining the role, royal expert Marlene Koenig said: "Catherine's role will certainly change as she will be the consort of the sovereign.
"There is no real constitutional role for a consort, just by tradition.
“She will be the first lady of the land, in terms of precedence."
When William and Kate become King William and Queen Catherine, their oldest child Prince George will become the Prince of Wales.
