The photographer Anwar Hussein, who has died aged 85, was integral to transforming the public image of the British royal family: from the aloof and unknowable to something more human. His photographs will also forever be synonymous with the brief life of Diana, Princess of Wales, but his work was much more than that.

Hussein hailed from what is now Tanzania, but his career began in earnest in the UK in the late 1960s, and his talent led to commissions for portraits of the pop and rock gods of the 70s: Marc Bolan, Elton John, David Bowie, Mick Jagger and Freddie Mercury. Soon Hussein realised he needed a fresh challenge. He wanted to record something more historic, more lasting, and he set his sights on the most exclusive family in the world: the House of Windsor.

As an African-born Muslim, Hussein faced many institutional and cultural obstacles. Back then, the go-to look of a royal photographer was clean-shaven, short back-and-sides and a blazer. Hussein was bearded, wore his hair long and favoured a leather jacket and cowboy boots. The fact that the royal entourage were sceptical, and often told him he stood no chance, made him all the more determined. He needed to break into the clique and bring the counterculture to the establishment.

He studied official photographs and found them too posed and contrived, knowing that if he combined the photojournalism techniques he had honed in Africa and on the streets of swinging 60s London with his experience engaging with the divas of film and music, he could show the Windsors in a new light.

When covering royal events for news outlets, he used a longer lens so as not to be obtrusive, which allowed his subjects to relax. The resulting candid, naturalistic images captured moments in between poses, such as Queen Elizabeth II corralling her corgis at Aberdeen airport in 1974. They also brought him to the attention of a Buckingham Palace that was keen to show the royal family in a more modern, relatable way.

By the end of 1976 Hussein had earned the trust of the Queen and Prince Charles, and he was invited to travel the world documenting royal tours of Africa, Canada, and New Zealand.

The greater Hussein’s access, the more intimate the pictures, and the greater the public’s interest became. Then Lady Diana Spencer burst on to the scene and royal mania took hold. Hussein had photographed her before at social events, but following her engagement to Prince Charles in 1981 the symbiotic relationship between the princess and the photographer began.

Hussein’s sensitive work helped propel Diana to become the most photographed woman in the world, and he captured some of the most memorable and important photographs of the “people’s princess”. He was there when she shook hands with an Aids patient in London in 1987, a landmark moment in the fight against the disease. He photographed her cradling a terminally ill child at a cancer hospital in Lahore in 1996, an image of palpable compassion, and Diana’s favourite photograph, though she was upset to learn the child died shortly afterwards.

As her marriage disintegrated, Diana used the power of photography to signify her unhappiness and isolation. This was epitomised by Hussein’s memorable 1992 shot of Diana sitting alone in front of the Taj Mahal, a building that symbolises enduring love.

“She showed her moods in the way she dressed,” Hussein said – and never more so than when she wore her “revenge” dress to a Vanity Fair party at the Serpentine Gallery in 1994. It was the same day that an ITV documentary disclosed that her estranged husband had admitted to committing adultery. She had bought the Christina Stambolian dress three years earlier, but had initially deemed it too risque for a woman in her position. That evening Hussein was there to capture her “looking like a million dollars”.

Hussein was devastated by the death of Diana. They had become friends, and she often confided in him. On a private plane, at a time when she was dating the surgeon Hasnat Khan, Diana asked the photographer about his interfaith marriage (in 1978 Hussein had married Caroline Morgan, who worked in publishing), and about Islam.

Hussein wrote and contributed to many books on the Windsors, and in 2021 his hugely successful exhibition of photographs, Princess Diana: Accredited Access (which included work by his two sons, Samir and Zakir, who both followed in his footsteps), was launched in Los Angeles and toured the world, closing in London in 2024.

Hussein was born in Chunya in what was then the British colony of Tanganyika, the fourth of the five children of Mohamed Hussein and Sardar (nee Begum). The family moved to Mwanza on the shore of Lake Victoria, where his father worked as a civil servant for the British government. There Hussein attended the local Indian public school, but education was not for him, and he left at 16. Instead his passion was for the camera he had borrowed from his elder brother, Akhtar, who owned a small photo shop in the town. Hussein taught himself on trips to the Serengeti plains, where he photographed the wildlife.

Aiming to earn a living as a photographer, he began to tout for work, and in his early 20s the United Nations commissioned him to document the humanitarian crisis in the Republic of the Congo, where conflict raged following its independence from Belgium. The work there cemented his love for photojournalism, and he decided to move to the UK to pursue his dream.

Arriving in 1963, Hussein initially struggled to find work and accommodation. From a tiny flat in Notting Hill, he lived hand-to-mouth until his breakthrough in 1968. He was documenting an anti-Vietnam war protest outside the American embassy in London when he photographed a police officer being dragged from his horse. He knew he had a great shot and hurried to the Daily Mail, where he persuaded them to develop the film. The result appeared on page one the following day.

He was then hired to cover news events and music festivals, and he began to take celebrity portraits. Hussein wanted his work to be published in magazines, where the display and pay were better than newspapers, so he switched to colour film.

He worked as a stills photographer for movie companies and photographed Sean Connery and Roger Moore on the sets of Diamonds Are Forever and Live and Let Die. Hussein knew how to hustle too. In 1970 he went uninvited to the set of Steve McQueen’s film Le Mans. He quickly built a rapport with McQueen and was given a small role as himself in the film. The star then invited Hussein to work on his next film, Papillon.

In recent years Hussein had begun to wind down, and the coronation of King Charles III in 2023 was his last job. He documented the lives of the royal family for more than five decades and, despite the initial naysayers, he was the longest serving royal photographer. As a child in Tanganyika he had only ever seen the British monarchs on postage stamps and, many years later, it was his photographs that would adorn the Royal Mail’s stamps.

He is survived by his wife, his two sons, four grandchildren and his sister Tasnim.

• Anwar Hussein, photographer, born 3 November 1938; died 23 September 2024