Had Elvis lived, he would have been 72 today. On the 30th anniversary of The King's death, Lindsay Jennings looks at the thousands who just can't help believing that he's still alive.

'I WAS in line at Costco waiting to purchase a Nathan's hot dog when I heard the customer behind me softly singing Love Me Tender," writes Cherry Fereday, of Dorris, California in the US. "I turned around to compliment him on his singing voice and that's when I realised it was The King. I was too nervous to say anything so I waited for him by the condiment table. As Elvis was adding mustard and relish to his dog, I asked him for his autograph. He gladly obliged and even gave me his cell phone number. I've called him a few times but he hasn't returned any of my messages."

This is message number 727 on The Elvis Sighting Bulletin Board. The internet site was set up as a "public service" six years ago for people wanting to log their accounts of running into the, presumably still, big man. According to the site, he has been spotted across the world, in America, Britain, Sweden, Japan, Hungary... even Sunderland. He makes an appearance every five days or so.

His favourite places include burger joints, supermarkets and at shopping malls. Some messages have an air of desperation - "he seemed so sad or lonesome. Good luck Elvis, wherever you are" - but most, in particular those from the Brits, are intent on seeing the funny side:

"I saw Elvis sitting in the birdbath behind my house. It's a rather large birdbath. I asked him 'why'? He said he was a bird lover and often liked to bathe with them. I made sure there was enough bird seed for them all and wished him well."

It is 30 years ago today since The King died, but his legend undoubtedly still lives on - with millions of dollars still being made. Elvis Presley Enterprises makes $40m every year from royalties and visitors to Graceland. On this 30th anniversary, there will be box sets reissued, films re-released, magazines launched, memorabilia sales...

But there are those who take their Elvis worship to another level. They believe he is still strolling among us in his blue suede shoes. There is even an Agency for Conformations and Registration of Sightings in America, in California, which sounds like a department within the Ministry of Magic from Harry Potter.

Amid stories of drug addiction and binge eating, Elvis officially died from a heart attack and was found on the bathroom floor of his Graceland home on August 16, 1977 by his 20-year-old fiancee, Ginger Alden. Both the autopsy and a review in 1994 blamed the heart attack, but it was later reported that between January and August 1977 he'd had almost 200 prescriptions made out for him, consisting of 10,000 pills.

At the time of his death, Elvis had had 81 gold-selling albums, had entered Billboard's Hot 100 pop singles chart 149 times and made 31 films as an actor. His funeral was attended by more than 75,000 fans and his death was felt across the world. But it was his iconic status and early death which would prove the ideal fuel for the conspiracy theorists.

The primary theory is that he faked his own death to live a peaceful life away from the public's adoring gaze, from the stress of the music business and from the drugs which dominated his latter years - pills to help him sleep, pills to keep him awake, pills to help him lose weight.

The 'evidence' in support of these suspicious minds is flimsy at best. Hours after Elvis's death, a man by the name of John Burrows, the name used by The King when travelling, was said to have bought a one way ticket to Buenos Aires. Elvis was said to have used this name on a trip to the FBI in Washington when he'd offered to inform on celebrities' illegal behaviour. Could he have informed and now be in a witness protection programme?

Others point to his grave, where Elvis's middle name, Aron, is misspelled as Aaron. The double 'a' in Elvis's name was removed after his twin brother Jesse Garon was stillborn and his parents had the name changed on Elvis's birth certificate. But critics argue that his father had 'Aaron' carved into his tombstone because he knew his son always wanted to change it to the traditional spelling. They also point out that there are any number of Elvis impersonators who could be mistaken for him.

Dr Joan Harvey, a lecturer in psychology at Newcastle University believes it is The King's vast legacy which has kept him in our hearts. "They're not wanting to believe that the image, the fairy tale, is dead, but then it isn't anyway because of this huge legacy that he left behind," she says.

"I think the number of people who genuinely believe he is still alive are few. Most of them are preserving an image and they might be wanting to see something spiritual in it. But the idea he's still alive at the age of 72, with arthritis and a croaky voice, it's a spiritual rather than a real belief."

But that hasn't stopped the believers hoping beyond hope that they may be right. Perhaps it's time to look at the queue behind you the next time you're in McDonalds or picking up a bag of frozen peas in the supermarket. You never know. there could be a tubby 72-year-old with a black rinse and long, long sideburns sporting a pair of blue suede shoes standing next to you...

On the other hand, he'll probably answer to the name of Bob and hail from South Bank, Middlesbrough.