Showing few signs of slowing down, Queen Elizabeth II -- Europe's longest serving monarch -- marks her 80th birthday on Friday with a host of parties and engagements that run until June. It looks set to be a colourful affair as the royal family enjoys a period of calm compared with a decade ago, when divorce and scandal put the House of Windsors in the headlines for all the wrong reasons. But the celebrations will also be on a smaller scale than a four-day party thrown for Queen Elizabeth's golden jubilee in June 2002, as her 80th birthday is seen as more of a private than a public achievement. "The queen's 80th is a landmark personal anniversary," said a spokeswoman for Buckingham Palace. "It's right that it should be appropriately celebrated."