Queen Elizabeth and Princess Margaret shared a deep and unbreakable bond throughout their lives, standing by each other through both highs and lows. 

Despite their contrasting personalities, Elizabeth was a protective older sister to 'Margo,' while Margaret affectionately called the Queen 'Lilibet'.

Margaret, who passed away 23 years ago yesterday, often expressed that her role in life was to support the Queen, and the sisters spoke on the phone daily. 

However, their relationship was not without its challenges. 

At times, tensions arose between them, and according to Andrew Morton, Margaret's attitude sometimes revealed 'a resentment and indifference that seemed almost ill-mannered'.

The bestselling author writes in his book, Elizabeth & Margaret: 'She could and would say things to the Queen and, for that matter, the Queen Mother that had even long-serving courtiers shaking their heads. 

'In turn, her sister and mother rarely reacted with anything other than calm equanimity. 

'They had seen and heard it all before - and then some.'

Mr Morton describes Margaret's questionable behaviour at a state banquet in 1957. 

During the event, a government minister complimented the Queen on her evening dress, prompting Margaret to remark: 'Darling, that does show your bosom too much.'

On another occasion, while at a barbecue at Balmoral, Margaret threw a wet dishcloth at the Queen's face. However, her sister simply ducked and continued clearing up. 

'She had learnt not to show too much concern as it merely pandered to Margaret's dramatic nature,' Mr Morton writes. 

Similarly, during an afternoon tea visit, the Queen found Margaret in a 'curmudgeonly mood,' despite the presence of her lady-in-waiting, Lady Glenconner. 

Margaret insisted on listening to The Archers and silenced the Queen whenever she tried to speak, saying, 'shhhh'.

Mr Morton explains: 'It was just like the old days in the nursery, though this time, rather than Crawfie, Lady Glenconner took control, firmly telling Margaret, "Ma'am, the Queen is here, and she can't stay all that long. Would you like me to help pour the tea?"'

Lady Glenconner then switched off the radio, poured the tea, and left the room.

Margaret was known for her lively social life, but as her health declined, she withdrew from socialising. 

'Now dependent on others to help her with the simplest tasks, she felt embarrassed and undignified,' Mr Morton pens.

'As her cousin Margaret Rhodes put it: "All her life she has been the sparkling one, but since her [first] stroke three years ago, she has lost that particular facility to sparkle."'

Previously fond of male company, Margaret now preferred the companionship of a few close female friends who would visit and read to her.

She once asked Anne Glenconner to read aloud from a book about plant seeds by the British gardener Roddy Llewellyn.

Although Lady Glenconner found it somewhat dull, Margaret was 'genuinely thrilled by the topic and urged her friend to continue'.

Margaret made a rare public appearance for her mother's 101st birthday celebrations at Clarence House.

According to Mr Morton: 'Both the Queen and QM tried to dissuade her from attending, as they felt that she would be upset by the reaction of people to her appearance'.

She insisted, however, on being there, although 'she looked a sad, pathetic shell of the glamorous, vibrant woman she once was'.

Seated in a wheelchair and wearing dark glasses to shield her eyes, Margaret seemed to take great joy in the occasion. 

She was 'happy to support her mother on her big day for what turned out to be the last time'.

That Christmas and New Year, Margaret stayed with the family at Sandringham but largely kept to her room and refused to eat. 

Mr Morton explains: 'For the most part, Margaret preferred to be on her own and refused to even speak on the phone to members of her family,' as she struggled with her emotions.

'For a time, Margaret did consent to speak to Lord Snowdon on the phone, and Roddy Llewellyn came to visit,' he continues.

'But towards the end she refused to allow any male visitors, saying: "I look so awful now."

'At one point, Margaret complained to her maid: "If only I were a dog, I could be put down."'

On February 8, 2002, Margaret suffered another stroke and passed away the following morning at King Edward VIII's Hospital, with her children by her side. 

Her coffin was placed in her bedroom at Kensington Palace, 'surrounded by her favourite photographs, sea shells and other cherished artefacts'.

The Queen visited for 'a few solitary moments' to say her final goodbye. 

Draped in her standard and adorned with a bouquet of white lilies and roses, Margaret's coffin was transported to the Queen's Chapel at St James's Palace, a twelve-minute journey led by Scottish pipers. 

On the day of her funeral, February 15, the Queen Mother was flown from Sandringham by helicopter and taken to St George's Chapel, Windsor, in a wheelchair.

Margaret's rose-coloured coffin rested at the altar as the organist played melodies from Swan Lake - a touching tribute to her love of ballet. 

She had carefully planned every aspect of the service, including the music, prayers and hymns.

It was Margaret's final wish to be cremated - the only way she could rest alongside her father at St George's Chapel, as there was no space left in the royal crypt. 

She was cremated at Slough Crematorium, becoming the first royal in over sixty years not to be buried. 

After the service, the Queen Mother, with 'great difficulty,' managed to rise to her feet in a final, sorrowful acknowledgment of her daughter. 

Mr Morton describes the Queen as deeply affected by the loss of her sister: 'As the coffin was placed into the hearse, one hand gripped that of her niece, Sarah Chatto, the other brushed away a tear.

'Out of the stillness came the sound of a Scottish lament, Desperate Battle of the Birds, chosen by Margaret's daughter. 

'It served as a metaphor for her tumultuous life, so full of promise and glamour yet dwindling into loneliness and despondency.'

Indeed, the Princess was renowned for her vivacious personality, but 'less well known to outsiders was that she dedicated her life to serve her sister and to uphold the values of monarchy that her sister represented.' This was a characteristic that the Queen appreciated in 'full measure'.

The guest list consisted of several celebrities, who knew Margaret personally, with no politicians or dignitaries present. 

After the service, the Queen pulled Anne Glenconner aside to thank her for introducing Roddy Llewellyn into Margaret's life. 

'She told her: "I'd just like to say, Anne, it was rather difficult at moments but I thank you so much for introducing Princess Margaret to Roddy, he made her really happy."'

Mr Morton highlights how this was a remarkable change of heart for the Queen, who had once banned Mr Llewellyn from her residences and had tried to prevent him from attending Margaret's fiftieth birthday party.

'It seemed as though the Queen had learnt, through her own travails with her children and their marriages, to be more accepting and understanding of others.

'She had been judgmental of her sister's relationship with Roddy, even though, as she now came to appreciated, he stood by her through the good times and, towards the end, the bad.'