Being on the cusp of adulthood and having a parent fish out your old baby photographs for visitors is embarrassing enough.

So imagine seeing yourself grow up on a film screen, and knowing that millions of others have watched you too.

Dakota Fanning says that seeing I Am Sam, Man on Fire or even War of the Worlds is like watching a stranger.

“It’s like, ‘Who is that?’ It’s like home movies, or the naked baby photos. I’m like a different person. I’m so little,” she laughs.

Now 18, Georgia-born Hannah Dakota Fanning has been acting since she was five, first in a TV advert then appearing as a young car crash victim in ER.

Guest appearances followed in other prime-time shows such as Ally McBeal, Ellen, Friends and CSI.

In 2001 she made her film debut in I Am Sam, depicting the daughter of a mentally vulnerable man played by Sean Penn. She won a Critics Choice Award for Best Young Actor and the role marked her out as precocious talent.

Since then she has worked with Denzel Washington and Tom Cruise before easing her way into transitional teen roles with projects like the Sixties-set The Secret Life Of Bees and Seventies biopic The Runaways – about the all-girl rock band – alongside her Twilight co-star Kristen Stewart.

Dakota has successfully seized every career opportunity offered to her, something that would be applauded by Tessa, the character she plays in Now Is Good.

An adaptation of the book Before I Die, Dakota is 17-year-old Brighton girl who’s been diagnosed with terminal cancer.

Determined to make the most of the time she has left, she draws up a bucket list of experiences to try before the end.

Director Ol Parker has described it as an ideal date movie as young girls will be weeping into their boyfriends’ shoulders (and the boys might find themselves swallowing the odd throat lump)

“It’s certainly emotional and can be upsetting at times but I think it has a really good message and is sort of hopeful in a weird way,” says Dakota.

“Tessa is the same age as me. As well as suffering from incurable cancer, she is coping with all the things you dream of doing in your life, being with friends, drinking, having a boyfriend, and she wants to get them done in the short time she has left,” she explains.

“Obviously being a young woman myself and knowing what girls dream will happen and knowing that none of those things will is a really, powerful intense thing.”

Remarkably, Dakota says she managed to stay dry eyed throughout filming.

“Tessa has to stay kind of strong and is a little bit hardened throughout, so I feel like I was kind of that way too.

“But I definitely know many men have had something in their eye a few times while watching.”

Among them was Jeremy Irvine, who is Adam, the handsome new neighbour Tessa falls for who is already grieving the loss of his dad.

Fresh from Steven Spielberg’s War Horse, this was 22-year-old Jeremy’s second movie.