As a boy growing up in the 60s and 70s, I was obsessed with cetaceans, the group of mammals that includes whales, dolphins and porpoises. Orca in particular fascinated me, with their glossy black and white markings, so sleek and streamlined.
They had a magical quality, invested with power, grace and beauty and yet capable of great violence, tearing their prey - salmon, tuna, seals and even other whales - apart with their large teeth. I saw them as supreme emperors of the sea.
Once, my two younger sisters and I persuaded our parents to take us to Windsor Safari Park where, at last, I could see orca and dolphins up close. There, in a concrete tank, barely bigger than a municipal swimming pool, a trio of dolphins went through their paces, jumping through hoops and balancing balls on their noses. Their reward? A dead fish from a bucket.
I remember even then feeling uneasy. This wasn't the wildlife spectacle I'd expected from watching my favourite programme, The Undersea World Of Jacques Cousteau, on television. This was more like a circus.
Then the dolphins were cleared from the pool and the show's star, a male orca called Ramu swam in from his holding tank. Immediately, I saw that his dorsal fin - which in male orca rides a full 1.8m high and scythes through the water - had flopped to one side.
Ramu, like most orca in captivity, was suffering from dorsal collapse, a condition almost never seen in the wild. It was a visible sign of the stress of being held in captivity.
I'm still shocked when I recall what happened next. This amazing creature was put through the same routine as his dolphin cousins. He jumped through a hoop, balanced a ball on his nose, and was rewarded with a fish. I may have been a boy from suburban Southampton, but I realised this was wrong. Very wrong. Forty years later, Tilikum's sad fate only reinforces that point.
Orca are one of the most intelligent and longest-living species on earth. They are highly social, sentient mammals, capable of complex communication, and they appear to experience all the emotions we humans do - including grief.
Orca society is entirely matriarchal, and females can live to 100 years of age. Bulls stay with their mothers all their lives, and if a calf dies, she will mourn it for weeks, keeping its body above water as she swims for hundreds of kilometres.
They are also extremely adept predators, living in "tribes" in every ocean on the planet. Some will herd fish into ''bait balls''. Others target seals by driving themselves onto beaches where seals congregate.
This is learned cultural behaviour. These creatures are more like us than we might find comfortable, which is perhaps why Tilikum's death has had such impact.
Tilikum was caught off Iceland, in 1983. Aged 2, he was named after the Chinook word for "friend".
Initially, he was kept in a tank in Reykjavik, where, having had the freedom of the ocean all his short life, he was reduced to swimming in circles like a goldfish, or he would lie still at the surface of his tank listening for his family pod.
In 1984, Tilikum was taken to Sealand on Vancouver Island, Canada, along with two female orca, Haida and Nootka. His "transfer fee" was $1 million, a value almost entirely predicated on his ability as a stud.
Tilikum, however, was bullied violently by the females he shared a pool with; they saw him as a threat. On February 20, 1991, one of Sealand's trainers, Keltie Byrne, a 20-year-old marine biology student, fell into the pool. The three orca dragged her around and prevented her from surfacing. Tilikum's role in her drowning didn't prevent him from being sold on to SeaWorld in Orlando the following year.
Eight years later, on July 7, 1999, a young man named Daniel Dukes broke into the park and into the orca tank. His body was found the next morning, draped over Tilikum's back. The autopsy indicated that he had drowned, but his genitals had also been bitten off.
Then, on February 24, 2010, Tilikum's highly experienced trainer, Dawn Brancheau - a 40-year-old who had worked at Seaworld for 15 years - was addressing the audience during a live show.
Suddenly, the orca loomed out of the water and grabbed her by her pony-tail, dragging her to the bottom of the pool. As horrified families were hurried away, desperate attempts were made to save Brancheau. But she had drowned and had been scalped in the process.
And yet, despite these deaths, a year later, Tilikum - now, at more than 6.5m and weighing more than six tons, the largest captive orca on record - returned to performing, albeit with precautions.
Trainers no longer swam with orca, and were told to stay at least 45cm away from them at all times.
For the last five years of his life, Tilikum had been in poor health with a lung infection that proved resistant to treatment. When he finally succumbed this month, his death reignited the debate about how we treat such creatures.
We call them killer whales, but there is not a single record of an orca killing a human being in the wild. Yet in captivity - often in solitary confinement - Tilikum had been driven, it seems, psychotic by the conditions in which he had been kept.
The modern trade in killer whales began in 1965, when an orca was accidentally caught in fishing nets off Namu in British Columbia. Seattle Marine Aquarium bought the animal for $8000.
It was then towed south in a floating pen and marine biologists were astonished to find that the rest of the young orca's family - led by its mother - were following in a futile attempt to retrieve their stolen calf.
Since then, about 200 orca have died in captivity and Tilikum could have been just another one of those statistics. But the release of Blackfish in January 2013 changed all that, making clear the cost of SeaWorld and other oceanaria on whales and dolphins.
In one of the most heart-rending scenes in the documentary, a mother orca was recorded still calling for her calf, although it was already thousands of miles away, in captivity.
Other footage showed frustrated captive orca grinding their teeth to the bone on the hard edges of their pools. Grown men wept as they recounted what they had witnessed when taking young orca from their families. Tilikum's story was at the heart of the film.
In the months that followed, visitor numbers to SeaWorld in Florida, California and Texas dropped. The value of the company fell by 33 per cent and it lost $10 million in profits.
SeaWorld issued a robust response to the claims made in Blackfish, insisting its operations have an educational value, as well as conserving and rescuing animals that are endangered in the wild, and that its care of its marine charges was exemplary.
But although it is true that many people learned to love whales and dolphins after visiting these places, I believe such theme parks are outmoded in our age of natural history documentaries and virtual reality.
Last March, bowing to public pressure and spurred by California banning the practice, SeaWorld announced that it would stop breeding orca.
"Because SeaWorld hasn't collected an orca from the wild in almost four decades, this will be the last generation of orca in SeaWorld's care," Joel Manby, its CEO, promised.
Tilikum sired 21 calves - most of them by artificial insemination. It is a terrible indictment that 11 of his progeny have predeceased him.
Cetaceans are still being taken from the wild off Russia and Japan, and now sell for $150,000 each. Animal rights take second place to such huge profits for captive whales and dolphins in China, Turkey, the Middle East and the Caribbean. Japan alone has 52 dolphinaria. Even in Europe there are cetaceans still in captivity in France, Spain and the Netherlands.
And there's no happy ending for the more than 20 orca left behind at SeaWorld's three parks. Unfit for release into the wild, the best these creatures can hope for is a dignified retirement.
Animal rights campaigners are calling for them to be allowed to live in contained sea pens in some semblance of the ocean wilderness that should be their habitat. SeaWorld does not agree, and will continue to use them in live shows, now billed as educational "encounters".
I've been lucky enough to see whales and dolphins all around the world in their natural environment. I have looked into the eye of a whale - and it has looked back at me, with curiosity, and sentience. I am convinced of their great intelligence.
They are one of nature's wonders and they are under enormous threat. Personally, I will never visit an oceanarium again.
Professor Philip Hoare, of the University of Southampton, is the author of The Whale and also The Sea Inside.
