What are we really feeling when we grieve for celebrities like Princess Diana who we have never actually met?
The preoccupation with the 20th anniversary of Princess Diana's death has refocused our minds on where we were, what we were doing and how we reacted when we heard of her tragic passing in the early hours of August 31, 1997.
Many had followed her life from shy nursery assistant to global superstar and felt her loss as keenly as if it had been a family member. That she died in such a violent manner made it all the more shocking to absorb.
In the BBC's documentary, Diana, 7 Days documentary about the immediate period following her death, aired this week, her sons William and Harry repeatedly mentioned the uncontrollable wailing from crowds as they followed her coffin on its final journey to Westminster Abbey. They recalled their childish confusion at the response as none of them had known her and she was their mother, and they weren't crying but put on their "game faces" as duty demanded.
The public, many of whom had camped out for days, were finally sharing their grief with the family of the woman they believed they knew. They'd had a piece of her for so long and wanted to vent, find a target for blame and express their deeply-felt loss.
All for someone they had never actually met in real life.
Twenty years before that, they were doing exactly the same for Elvis, gathering at Graceland in disbelief and shock at his sudden young death. Then John Lennon (New York's 'Dakota' building where he had lived and was shot instantly turned into a shrine), Michael Jackson, latterly David Bowie and the countless others who we believe are iconic in some way. And there isn't a God-fearing Irish granny who can't tell you, probably followed by a sign of the cross, when they first heard the news about John F Kennedy's murder.
Among the common reactions we feel when a sudden death occurs, according to bereavement experts, are anxiety, anger, numbness, depression, denial and a fear of dying ourselves.
Many ordinary people saw a part of themselves in Diana: perhaps they had children the same age or their own marriage was a bit rocky. Maybe she just provided sparkle in an otherwise ordinary life.
Andrea Koenigstorfer is a senior psychotherapist with Insight Matters Counselling. She says similar stages of grief are felt when a beloved celebrity dies as with a family member. "Celebrities represent something to us, they've achieved things we might never achieve, and we identify with them. They give us hope. Just think of the hype around Conor McGregor and all the young kids aspiring to become famous MMA competitors - it gets them believing in the future and their abilities. And then imagine such a person dies.
"We grieve the loss of the person, the connection with them, but also a little bit of the life experience you had of watching them perform, the experience of being part of their lives in a way. They're giving you emotions, things to talk about and all of a sudden that's gone."
That goes some way towards explaining the visceral, almost ferocious reaction which caught even hardened journalists by surprise. That their needs and feelings were only voiced by that master of political ballet dancing, newly minted Prime Minister Tony Blair, made it worse and it wasn't long before demands for redress followed.
There was also guilt. In the initial rush to pin her death on the paparazzi, did we equate our unending thirst for magazine covers with the provenance of pictures of our favourite idol?
When the 'blame' moved to the Royal Family, Britain's Queen Elizabeth was considered unemotional, uncaring and 'not there'. But why should she be there for Joe and Mary Bloggs when she was needed for her grandsons?
Do we believe our celebrities to be somewhat invincible, immortal? Their enduring fame bestows an artificial halo around them, so that we forgive the negative qualities we never get to live with, while extolling the public persona we yearn for.
Up until a few years ago, a celebrity or presidential death was generally announced on the most immediate medium available - radio - in sombre tones as journalists and programme makers scrambled to cobble together meaningful obituaries in time for the next bulletin or newspaper.
These days, of course, you're far more likely to see the shocking news first on Twitter or Facebook. Does that change our reaction?
Stephen O Leary, Managing Director of social media analysis firm Olytico, says: "For many people, social media and Twitter, in particular, is one of the first places a death is announced, but there's a long history of rumours and mis-reporting of celebrity deaths online, so going to traditional media and breaking news services is still important for confirmation. Michael Jackson was probably the first time social media was used as a memorial site - it was a watershed moment for that kind of news to be shared in this way."
In terms of reaction, social networks can offer a place for sharing feelings, says O'Leary. "People always did this, but the platform for it has changed. Sometimes it can be the person's name and RIP; for others it's memories, photos, video posted in the hours, days and weeks following the news, and which recurs on anniversaries such as we're seeing with Diana.
"When another iconic princess (Leia), aka Carrie Fisher, died last December, she was mentioned in 5.6 million tweets during the first 72 hours. This year, the celebrity death which has created the biggest reaction so far was Chester Bennington, frontman for rock band Linkin Park who was mentioned in 4.9 million tweets immediately after his demise."
That he was just 41 years old undoubtedly contributed to that. Koenigstorfer agrees. "People now have a public way of grieving a person's death, a tool in the grieving process, where they are less isolated in how they feel. It may be harmful as in there may be people that are too easily influenced by others, and then caught up in behaviours like suicide or self harm - the ripple effects can be massive.
"There's no recipe for a proper way of grieving. There's no schedule or right or wrong. It's a very personal and individual thing. We don't just cop on or get over a loss, we learn to cope with it and adjust, and one way of doing that is sharing and venting, and seeing that other people feel similar or the same."