Britain's Queen Elizabeth and the Duke of Edinburgh celebrate their 65th wedding anniversary today (20.11.12).
The British royals reach their Blue Sapphire anniversary today, but have opted for a low key affair, spend the day privately together.
The couple will then continue with their royal duties for the week, which include a joint visit to Bristol on Thursday (22.11.12) and official engagements for the Duke tomorrow (21.11.12) and on Friday (23.11.12).
The royal marriage sets a new precedent, as no royal couple in British history have stayed married for as long.
The queen and Philip first met in 1939 while she was a teenager and he a naval cadet, and they later became pen friends.
They married at Westminster Abbey in 1947, and the queen had to use ration coupons to buy the material for her dress, which was designed by Norman Hartnell.
While she had to be frugal in her preparation, the goodwill of others knew no bounds and the happy couple received 2,500 gifts from Britain and the Commonwealth.
From their honeymoon, Philip wrote to Queen Elizabeth, the Queen Mother: "[Elizabeth] is the only 'thing' in the world which is absolutely real to me and my ambition is to weld the two of us into a new combined existence that will not only be able to withstand the shocks directed at us but will also have a positive existence for the good."
Sarah Bradford, the queen's biographer, said the letter is an indicator of why their marriage has lasted so long.
She told the Daily Telegraph: "He talked in that letter about his love for his wife and of how they were thinking the same way about things.
"They both appreciate each other, love each other, like each other and I think they also both appreciate the position that they occupy and their responsibility.
"You don't just pop in, marry the queen and pop off again."