The Queen and Princess Margaret: Loyal sisters and King George VI's pride and joy

Princess Elizabeth was just 10 when her family's quiet life was thrown into turmoil.

Edward VIII, who had been King for less than a year, caused a constitutional crisis by announcing his wish to marry an American divorcee and to renounce the throne.

It meant that Elizabeth's father was now King George VI - and that someday she would be Queen.

But where did that leave her younger sister Princess Margaret? Suddenly the focus was on her big sister, who was four years older. Margaret would often say her role in life was to "help the Queen".

The pair had been inseparable. Growing up, they had little contact with other children, being educated at home. They relied on each other for company, whether it was for a morning swim at the Royal Lodge in Windsor or to take their beloved dogs Dookie, Spark, Flash, Scruffy, Mimsey and Stiffy for a walk.

They even dressed the same. The American ambassador noted during a visit in 1938 that they were wearing identical rose dresses with checked blouses, red shoes with silver-coloured buckles, white socks and necklaces of coral and pearl.

Consciously or not, Elizabeth began to live up to people's expectations - described as serious and dignified. Her little sister, however, had no such responsibility.

Their father would say that Elizabeth was his pride, but her sister Margaret was his joy. She was always the lively, unpredictable one, with the ability to make people laugh.

Despite their differing roles, the princesses were still close. The crunch came when the King died.

The Queen, as head of state, was thrown into an endless round of duties, and Margaret had to leave Buckingham Palace and move to Clarence House with the Queen Mother.

Margaret was left bereft of her sister after losing the father she adored.

It was at this time she relied more heavily on her secret relationship with Group Captain Peter Townsend, an older, handsome - and married - man. He divorced his wife and proposed to 23-year-old Margaret in 1953, but the establishment resisted the idea.

This all happened around the time of the Queen's coronation at Westminster Abbey.

She was left to decide what to do about her sister's romance. Margaret had to be 25 years old to marry without the sovereign's permission. After that she needed parliament's approval.

As Head of the Church of England, the Queen was told that the idea of her sister marrying a divorced man 15 years her senior was shocking and unacceptable. Not wanting any adverse publicity, Elizabeth asked the couple to wait another year.

While Princess Margaret and the Queen Mother were on a lengthy tour of Rhodesia, the politicians acted.

Peter Townsend was abruptly and deliberately found a new posting abroad and the princess was offered a stark choice: If she still wanted to marry Peter Townsend, she would have to give up her royal status.

The princess called off her engagement and involved herself with royal duties, in support of the Queen.

Elizabeth always remained protective of her sibling and worried about her. When it was suggested later, after the collapse of the marriage to the Earl of Snowdon and her affair with the much-younger socialite Roddy Llewellyn, that Margaret be stripped of her Civil List privilege, the Queen staunchly defended her.

But their friends were by that stage quite different. While the Queen enjoyed traditional country pursuits, Margaret was more often pictured going to glamorous cocktail parties, mixing easily with the stars, a fur draped seductively around her shoulders, and smoking with a long cigarette holder - the epitome of decadence.

In her life Margaret was torn between royal duty and her own personal happiness - but throughout the sisters remained close and loyal to each other.

Princess Margaret died of a stroke in 2002 at the age of 71.