19: Too old for angst. Too young for fear

Replace a legend, score a hat-trick, inspire a famous victory? No problem, boss. Theo Walcott, who did all of those things for the England football team in Croatia last Wednesday, is at an age when everything can seem possible.

Nineteen. You're young and full of energy, but have a bit of experience, too. The angst of the teenage years is nearly over, and the trials of full adulthood have yet to come. For some people, 19 is a golden age: for Theo and Becky and Britney and Elvis, to name but three of the 19-year-olds celebrated here.

(And yes there are 19 of them. And no mention of "19" by Paul Hardcastle, the scratchy Eighties pop hit that will have some readers who have not been teenagers for a very long time muttering "N-n-n-n-nineteen" to themselves. The song relates to the average age of a combat soldier in Vietnam. Not much to celebrate there.)

Everyone on the list had their big breakthroughs or their best years just before turning 20. Some went on to greater things. But for others, 19 was as good as it ever got. Is it a coincidence that so many high achievers seem to make their first splash or reach their peak at this age? Dr Arthur Cassidy, a social psychologist specialising in teenage development, says not.

"Some 19-year-olds are very precocious – they see the world as their oyster," he says. "They have more maturity than younger teenagers and are beginning to look for older role models. But they still have a great optimism." These successful ones are free of much of the angst of the teenage years, having established who they are, what they can do and how they fit in with the world. They are also free of the cares of full adulthood, which have not yet sunk in.

Soon they will go from being startlingly talented teenagers, ahead of their peers, to immature twentysomethings, behind the field. That is "one of the great transitions of life," says Dr Cassidy, and it can be very difficult. With it comes a greater realisation that others are at least as talented. But at 19 it often still lies ahead. Identified as being gifted – at sport, music, science or whatever it is – prodigies have often been hothoused and sheltered by older adults with high expectations.

"Some feel trapped," says Dr Cassidy, an expert in self-harm and suicide among gifted teens. But some thrive.

Theo Walcott dealt remarkably well with the hysteria that surrounded his being chosen for the England World Cup squad in 2006 even though he had never played a game for his club, Arsenal. And he seemed to cope as well last week with his new status as the successor to David Beckham, saying he would just carry on "going in to work".

His secret may be nice lobes. The frontal lobes, which control decision making and risk evaluation, are the last part of the brain to develop fully in a young adult. At 19, the experts say, they may have grown enough to bring calm and a certain maturity, but not so much that they are shrieking, as they do with age: "Oh no, you can't do that – it's much too risky or difficult."

So Theo skips down the wing and bangs in the goals against a side England are not supposed to be able to beat. So Becky Adlington destroys the opposition in the Olympic swimming pool. So Elvis Presley accidentally creates a sound that will change the world. Just like that. While life is still uncomplicated.

Good on them. Fantastic. Let's rejoice for all the precocious, high-achieving 19-year-olds. Because boy oh boy (writes a weary grown-up), does life have some shocks in store later on...

Theo Walcott

Tipped as the future of English football two years ago, but it wasn't until his hat-trick last Wednesday – at the age of 19 – that he finally lived up to all the hype

Christopher Paolini

Was 19 when his Eragon fantasy stories were launched by a mainstream publisher. Made 'The New York Times' bestseller list that year, and got a film deal

Elvis Presley

Fooling about with the song 'That's All Right (Mama)' in a Memphis studio in 1954, Elvis came up with a sound that would change the world. Guess how old he was?

Martin Halstead

Called himself 'a baby Branson' when announcing the launch his own domestic airline, Alpha One, in 2005. False start. Still to get his plans off the ground

Marie Antoinette

Became Queen of France at 19, when her husband was crowned Louis XVI. Lived it up, having her cake and telling the peasants to eat it, but later lost her head

Helen Oyeyemi

Sent some of her writings off for advice and won a six-figure book deal. Finished her first novel, 'The Icarus Girl', at 19

Mary Shelley

On a rainy trip to Lake Geneva with Lord Byron and her future husband, she turned a nightmare into a story. 'Frankenstein' gave birth to both horror and science fiction

Louis Smith

Another unexpected Beijing triumph. The Peterborough boy won bronze on the pommel horse, the first British individual gymnastic medal in a century

Rhys Jones

Got to the top of Everest just before turning 20, completing his attempt to climb the highest peak on every continent while he was still a teenager

Yizhu

Emperor of China at 19, in 1831. Known as Xian Feng, meaning 'universal prosperity', which was untrue of his empire. Drank, took opium, had a lot of sex. Lasted 11 years

Joan of Arc

Leading France to victory over its enemies? Good. Being burned at the stake at 19? Bad. Unless you believe yourself to be a martyr, and are destined to become a saint

Marilyn Monroe

Spotted by a photographer at 19. Within a year, Norma Jeane had changed her name, filed for divorce, dyed her hair blonde, joined a model agency and taken her first screen test

Johan Cruyff

One of the greatest footballers ever. Was 19 when he won the Dutch league with Ajax and made his international debut with Holland

Adele

Debut album released in January was called '19' after her age. It went to number one. By 20 she had played America and been nominated for the Mercury Prize

Lily Cole

At her peak last year, aged 19, the super-model was on the Rich List and starred in the remake of the St Trinian's movie. Now 20, she has gone to university

Alia Sabur

New York maths prodigy who became the youngest professor in history, according to 'Guinness World Records', when she was appointed by Seoul University earlier this year

Britney Spears

Became a star early, but 19 was her best year by far. Sold 1.3 million albums in a week, the most ever by a solo artist. Marriage, misery and head-shaving followed

Rebecca Adlington

Mansfield swimmer stunned the world and led the British gold rush at the Olympics this summer by winning two swimming finals in Beijing

Anya Hindmarch

Instead of going to college, went to Italy to learn about handbags. Returned and started her own shop in London at 19. Now one of the world's leading designers