It was an event I never expected to attend, but there I was on September 6, 1997, walking in bright sunshine to Westminster Abbey.

As hundreds of thousands of people massed in the area surrounding the historic church, I was on my way inside for the funeral of Princess Diana.

Just a week earlier, she had been tragically killed in a car crash in Paris at the age of just 36.

The death of the ‘People’s Princess’ – which I had covered as a royal correspondent – prompted an outpouring of grief among millions.

Literally hundreds of thousands of bouquets of flower had been laid outside her home at Kensington Palace, as well as Buckingham Palace and Balmoral in Scotland.

And the tears from around the world could have filled an ocean.

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Prince Charles, Harry and William, Earl Spencer and Prince Philip watch as the Guardsmen of the Prince of Wales Company of the Welsh Guards carry the coffin of Diana, Princess of Wales into Westminster Abbey, September 6, 1997

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Prince William wiping his eye after viewing the floral tributes to his mother, Diana, Princess of Wales, outside the gates of Balmoral

Inside the Abbey were 2,000 invited mourners. Outside, the official estimate was three million lining the route.

And around the world 2.5billion people watched the ceremony – which lasted for one hour and ten minutes – on television.

It was broadcast in 44 languages, and it was one of the biggest televised events in history.

The world literally stopped to pay its respects.

Diana was given a ceremonial funeral even though she was no longer a member of the Royal Family.

Soldiers from the Queen’s Life Guard marched each side of the gun carriage from the King’s Troop.

Prince Philip, Prince Charles and Princess Diana’s brother Earl Spencer walked behind Diana’s coffin in the funeral procession, along with Prince William and Prince Harry.

At the time, William and Harry were just 15 and 12 years old, respectively.

The decision to have her sons walk behind the coffin was and still is a topic of contention.

William confirmed in the 2017: ‘It wasn’t an easy decision, and it was a collective family decision to do that. It was one of the hardest things I’ve ever done.

‘But we were overwhelmed by how many people turned out, it was just incredible. There was that balance between duty and family and that’s what we had to do.’

Harry recalled: ‘I think it was a group decision. But before I knew it, I found myself with a suit on with a black tie and a white shirt, I think, and I was part of it.

‘Genuinely, I don’t have an opinion on whether that was right or wrong. I am glad I was part of it. Looking back on it now, I am very glad I was part of it.’

Prince Philip had allegedly told prime minister Tony Blair’s officials to ‘f*** off’ when the suggestion was initially made.

Among the non-royal attendees were Hillary Clinton, Steven Spielberg, Mariah Carey, Tom Cruise, Nicole Kidman, George Michael and Luciano Pavarotti.

Elton John sang a rendition of ‘Candle in the Wind’ during the service, with new lyrics written as a tribute to Diana.

The single became the best-selling since the UK and US singles charts began in the 1950s, with total sales exceeding 33million units.

In the Abbey, I sat just behind Mohamed Al-Fayed, who had lost his son Dodi – Diana’s lover – in the same car crash.

Opposite us were the Royal Family, led by the Queen.

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Mourners look at some of the floral tributes to Diana at Kensington Palace shortly after her death was announced

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Flowers and wreaths that no one could have imagined kept on being laid until there was a sea of them around Kensington Palace

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Princess Diana’s body was taken from St James’s Palace to Kensington Palace the night before the funeral

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Earl Spencer checking on his nephew, Prince Harry before the funeral procession

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Prince Philip stood by Prince William’s side and Harry had his father and Earl spencer either side of him as the brothers marched slowly behind their mother’s coffin

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The sight of Prince Philip, Prince William, Earl Spencer, Prince Harry and Prince Charles walking behind Diana’s coffin seven days after her death is one that no one who witnessed it will ever forget

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It was too much for this police officer as the funeral cortege passed her

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The Queen arrived separately and was greeted by a clergyman at the doors of Westminster Abbey

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The coffin followed by the boys and  their grandfather, uncle and father could barely be seen as hundreds of flowers had been put around the abbey

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The boys walked into the Abbey with their heads down, as Prince Charles looked heartbroken behind them

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On Diana’s coffin lay a small wreath with the word ‘Mummy’

One of the most poignant moments came when Earl Spencer delivered his heartfelt eulogy to his sister, which was beamed to the waiting crowds outside.

As he started, a shaft of light came through a window in the ceiling and lit up her coffin.

The Earl’s speech famously pulled no punches, strongly criticising the press and indirectly criticising the Royal Family.

As he finished you could hear a pin drop, then within seconds a thunderous applause which started outside the Abbey got louder and louder and protocol was ignored as the congregation joined in.

Then Diana’s coffin was driven to her family home, Althorp in Northamptonshire, in a Daimler hearse.

My good friend Paul Chopping, a police officer of many years, was given the honour of leading his motor bike unit – the Special Escort Group – on the route as he was about to retire.

Mourners cast flowers at the funeral procession for the entire 76-mile length of its journey and vehicles even stopped on the opposite carriageway of the M1 motorway as the cars passed.

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When Earl Spencer’s finished his eulogy, you could hear a pin drop, then within seconds a thunderous applause which started outside the Abbey got louder and louder and protocol was ignored as the congregation joined in

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A tearful Mohammed Al Fayed was seated just in front of Charles Rae, who himself had a cry after the service

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Elton John sang a rendition of ‘Candle in the Wind’ during the service, with new lyrics written as a tribute to Diana. The single became the best-selling single since UK and US singles charts began in the 1950s

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Tom Hanks, Tom Cruise, Nicole Kidman and Steven Spielberg were just a few of the famous faces who attended the funeral that day

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Paul Chopping, a police officer of many years, was given the honour of leading his motor bike unit, the Special Escort Group, on the route as he was about to retire

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Mourners cast flowers at the funeral procession for the entire 76-mile length of its journey

In a private ceremony, Diana was buried on an island in the middle of a lake called the Oval, which is part of the Pleasure Garden at Althorp.

The coffin bore a weight of a quarter of a tonne (250 kg) because it was lined with lead, as is tradition with British royalty.

Diana was dressed in a black Catherine Walker dress and black tights and was holding a rosary in her hands.

The rosary had been a gift from Mother Theresa of Calcutta, a confidante of Diana, who had died the day before her funeral.

As I walked the streets back to the office, the enormity of what had happened finally hit me.

Diana, who had been a big part of my life for around 15 years, had gone.

I found a quietish alley, and the tears started to well in my eyes. I know big, tough, Scottish blokes aren’t supposed to show their feelings, but hey, who would have guessed, eh!

I have never claimed to be one of Diana’s closest confidantes.

I like to think that I did my job professionally. Yes, I liked her very much.

She was a fantastic ambassador for Britain and a fantastic woman and mother. And the causes she devoted herself to never had a better ambassador.

Sure, she had her faults, but then, who doesn’t? It’s just her faults were laid bare in public because she was a high-profile celebrity.