The life of Queen Elizabeth, the Queen Mother spanned more than a century and she saw at first hand many of the key events in the last millennium's closing decades.

Her life came to personify how Britain changed in the 20th century; witnessing the slow decline of a global empire, two world wars and the social changes accelerated by the 60s that ended the age of deference - particularly to the monarchy.

Born on August 4 1900, Elizabeth Angela Marguerite Bowes Lyon came from Scottish landed gentry. The ninth of 10 brothers and sisters, her father was the Earl of Strathmore and Kinghorne.

Though born in London, she grew up on the family's estate at Glamis Castle and had a strong affinity for her Scottish roots.

Her idyllic childhood was shattered by the First World War which claimed the life of her elder brother, Fergus, who was killed in France at the battle of Loos. From the age of 14 she helped care for the wounded soldiers who were sent from the battlefront to convalesce at Glamis.

Marrying the second son of the king, the first "commoner" to become a royal for 300 years, should have meant a life of comfortable obscurity but the abdication crisis of 1935 changed her life forever.

Today the idea that a row over who should hold the throne would embroil the prime minister and create a national scandal is a quaint notion. But King Edward's abdication over his marriage to the twice divorced American Wallis Simpson rocked the establishment and put into question the future of the monarchy.

Prime minister Stanley Baldwin's negotiations with the Palace were complex and secretive, with the public largely kept in the dark. There were concerns that the then Duke of York was not strong enough to be king and the possibility of the crown passing to the Duke of Kent was touted in the press as an option.

The wife of the man who became King George VI in 1936 played a key part in finalising the decision and from then until her death she helped shape the "modern" public face of the monarchy.

With the onslaught of the Second World War came a public relations role - a Royal visit to America was part of Churchill's efforts to woo President Roosevelt.

Royal visits to the country's bombed cities became a part of the morale boosting efforts during the seven years of war, revitalising the public's affinity for the monarchy and defining her public profile.

Her final role as the Queen Mother came at the request of Winston Churchill and was one she continued for 50 years, driven by a sense of duty and public service.

Churchill argued that her daughter had ascended the throne at a very young age she could not shrink away from public life as Queen Victoria had done after the death of Prince Albert.

She went on to become the patron of 312 organisations and was the first woman to be chancellor of London University.

In later years she became increasingly at odds with the next generation of royals and the changing public attitudes to the monarchy. As a product of an Edwardian childhood, raised in the traditions of the aristocracy she was a staunch opponent to moves aimed at modernising the Royal Family.

With the end of the "nuclear family" and the diminished political importance of the monarchy has come a change in public attitudes and reverence. A series of Royal divorces and the death of Diana, Princess of Wales ended the fairytale image of the monarchy she had played such a direct part in shaping.

The Britain she leaves behind is very different to the one she was born into; socially, economically and politically. No longer the ruler of an Empire it is a country that still struggles with the idea of being "European". The rise of globalisation and advances in technology have changed the way we live, work and communicate.

As the modern monarchy prepares for the Queen's golden jubilee later this year, amid fears of public indifference, the woman many credit with the institution's post-war strength will be absent from the celebrations, as will her daughter Margaret, who died seven weeks ago aged 71.

The Queen Mother made an indelible mark on British public life, carving out a unique role for herself. Her death brings the end of an era personified by a remarkable person.

The nation is set for a 10-day period of mourning, with a funeral set for Tuesday next week in Westminster Abbey. Her body will be interred at Windsor, next to that of her husband.

The Palace has opened an online condolence book and other books have been opened at St James's Palace and at Holyrood Palace in Edinburgh.

Meanwhile, thousands of Britons are expected to pay their respects when the Queen Mother's coffin is brought later this week to lie in state in the medieval Westminster Hall, where it will be placed on a purple draped catafalque in the same spot where her husband George VI lay in 1952.

The first such Royal coffin to be placed on public view was that of Edward VII in 1910 - another figure whose reign defined an age.

The coffin which will be guarded by Gentlemen at Arms and Yeoman of the Guard is set to generate a queue of loyal subjects stretching from the Palace of Westminster towards Buckingham Palace. The Queen Mother is to be only the second Royal consort to lie in state in modern times, her mother-in-law Queen Mary was the first, in 1953.

Parliament and the devolved institutions in Scotland and Wales are to be recalled to allow MPs and other elected representatives to pay tribute. MPs will return from their Easter recess on Wednesday.