Among the members of the Royal Family throughout history, Diana remains one of the most popular and still continues to influence the principles of the Royal Family and its young generation. From her engagement to the Prince of Wales in 1981 until her death in 1997, Diana was a major presence on the world stage, often described as the "world's most photographed woman". She was noted for her compassion, style, charisma, and high-profile charity work, as well as her difficult marriage to the Prince of Wales. Her former private secretary mentioned her as an organised and hardworking person, and pointed out that the Princess's husband wasn't able to "reconcile with his wife's extraordinary popularity", a viewpoint supported by author Tina Brown. He also stated that she was a tough boss who was "equally quick to appreciate hard work", but could also be defiant "if she felt she had been the victim of injustice". Paul Burrell, who worked as a butler for the Princess, remembered her as a "deep thinker" capable of "introspective analysis". She was often described as a devoted mother to her children, who are influenced by her personality and manner of life. In the early years, Diana was often noted for her shy nature, as well as her shrewdness, funny character, and smartness. Those who had communicated with her closely describe her as a person who was led by her heart. The Princess was also said to have a strong character, due to the fact that she entered the Royal Family as an inexperienced young girl with little education but could handle their expectations and also overcome the difficulties and sufferings of her marital life.
Diana was widely known for her encounters with sick and dying patients, the poor and unwanted whom she used to comfort, an action that earned her more popularity. She was mindful of people's thoughts and feelings, and later revealed her wish of becoming a beloved figure among the people by saying in her 1995 interview that "[She would] like to be a queen of people's hearts, in people's hearts". According to the biographer Tina Brown, she could charm the people with a single glance. She also points out that Diana's fame had spread around the world, even affecting Tony Blair who reportedly had said that Diana had shown the nation "a new way to be British". During her life the Princess could build a relationship with ordinary people, which was shown in the messages sent by different individuals around the world as a tribute after her death. Diana is often credited for bringing the types of charity works carried by the Royal Family to a wider range and a more modern style, as well as affecting some of the household's traditional manners. Eugene Robinson of The Washington Post wrote in his article that "Diana imbued her role as royal princess with vitality, activism and, above all, glamour". Alicia Carroll of The New York Times described Diana as "a breath of fresh air" who was the main factor that made the Royal Family known in the United States. Despite all the marital issues and scandals, Diana continued to enjoy a high level of popularity in the polls while her husband was suffering from low levels of public approval. Her peak popularity rate in the United Kingdom between 1981 and 2012 was 47%.
Diana had become what Prime Minister Tony Blair called the "People's Princess," an iconic national figure. Her accidental death brought an unprecedented spasm of grief and mourning, and subsequently a crisis arose in the Royal Household. Andrew Marr said that by her death she "revived the culture of public sentiment". Her brother, the Earl Spencer, captured her role:
"Diana was the very essence of compassion, of duty, of style, of beauty. All over the world she was a symbol of selfless humanity. All over the world, a standard bearer for the rights of the truly downtrodden, a very British girl who transcended nationality. Someone with a natural nobility who was classless and who proved in the last year that she needed no royal title to continue to generate her particular brand of magic".
In 1997, the Princess was one of the runners-up for Time Man of the Year. In 1999, Time magazine named Diana one of the 100 Most Important People of the 20th Century. In 2002, Diana was ranked third on the BBC's poll of the 100 Greatest Britons, outranking the Queen and other British monarchs. In 2006, the Japanese public ranked Diana twelfth in The Top 100 Historical Persons in Japan.
Despite being regarded as an iconic figure and a popular member of the Royal Family, Diana was subject to criticism during her life. Patrick Jephson, her private secretary of eight years, wrote in an article in The Daily Telegraph that "[Diana] had an extra quality that frustrated her critics during her lifetime and has done little to soften their disdain since her death". Some have said that it was Diana who let the journalists and paparazzi into her life as she knew that they were the source of her power, thus she had "overburdened herself with public duties" and destroyed the border between private and public life. Diana was famously criticised by philosophy professor Anthony O'Hear, who in his notes argued that she was unable to fulfill her duties, her reckless behaviour was damaging the monarchy, and she was "self-indulgent" in her philanthropic efforts. Following his remarks, the Princess was defended by the charity organisations that were supported by her, and Peter Luff who called O'Hear's comments "distasteful and inappropriate". Further criticism surfaced as she was accused of using her public profile to benefit herself, which in return "demeaned her royal office". Diana's unique type of charity work, which sometimes included physical contact with people affected by serious diseases, in some cases, had a negative reflection in the media.
Sally Bedell Smith characterised Diana as unpredictable, egocentric, and possessive. Smith also argued that in her desire to do charity works she was "motivated by personal considerations, rather than by an ambitious urge to take on a societal problem". Eugene Robinson, however, said that "[Diana] was serious about the causes she espoused". According to Sarah Bradford, Diana looked down on the House of Windsor whom she reportedly viewed "as jumped-up foreign princelings" and called them "the Germans". She believed that Diana was a "victim of her own poor judgment" as she lost a social privilege by doing the Panorama interview. Some observers characterised her as a manipulative person. It was also alleged by some people that the Princess and her former father-in-law, Prince Philip, had a relationship filled with tension. Other observers, however, said that their letters provided no indication of friction between them. Author Anne Applebaum believed that Diana in fact hasn't put any impact on public opinions posthumously; an idea supported by Jonathan Freedland of The Guardian who also noted in his article that Diana's memory and influence started to fade away in the years after her death, while Peter Conrad, another Guardian contributor, argued that even in "a decade after her death, she is still not silent", and Allan Massie of The Telegraph described the Princess as "the celebrity of celebrities" whose sentiments "continue to shape our society".