Her son had told her to practise her "not too disappointed" face, but Nicky Singer was named a winner at a top award for children's writers.
A stunned Nicky said: "I had to quickly recompose my features into an utterly delighted face."
And there was a even bigger surprise in store - not only did she triumph in the Blue Peter Book I Couldn't Put Down award, she also scooped the coveted Book of the Year Award.
Nicky's double whammy came for her novel Feather Boy.
Nicky, of Ormond Road, Hove, said: "I was absolutely thrilled to win because although the shortlist for the awards is drawn up by adults, the children choose the winner.
"For a children's author, the biggest prize of all is that children like your work."
Feather Boy tells the poignant tale of schoolboy Robert Nobel - always the last to be chosen for the sports team and secure in the knowledge he will never get to date the prettiest girl in school.
Still reeling from his parents' divorce, he is constantly mocked and harassed by know-all classmate Niker.
However, Robert's life is revolutionised when, as part of a school project, he meets elderly Edith Sorrel who inspires him to solve a mystery.
In the process, he learns to conquer his own fears as well as the bullying Niker.
Nicky was inspired to write the book after witnessing her son Roland's enthusiasm for Harry Potter. She tested her ideas on him and he became her literary critic.
Venues in the book are also close to home - Chance House is in St Aubyn's and St Andrew's Church in Church Road and a lane in Connaught Road all feature in the book.
Nicky, 46, said: "It was Roland who advised me to practise my disappointed face.
"Unfortunately he couldn't come to the award ceremony at Television Centre because he was in a school production but my other children, Edmund and Molly, were there. Molly was jumping on her chair. I think they are proud of me."
Although Nicky has penned four previous books, this was her first foray into children's writing.
The grown-up panel for the Blue Peter awards was chaired by Ian Hislop, panellist on TV show Have I Got News For You?
Other judges included author Malorie Blackman, writer and illustrator Shoo Rayner, literature consultant Liz Attenborough and Blue Peter editor Steve Hocking.
The nine young judges were Blue Peter viewers.
Nicky's next book, Doll, will be out in March.
It is a "first love" story between a troubled girl and a Latin-American boy who has been adopted and brought to England.
Aimed at older teenagers, it will focus on difficult relationships, new love and hidden secrets.
She is now working on a third children's book called Heaven.
Picking up the awards enabled Nicky to achieve a lifetime ambition and visit the Blue Peter studios. However there was one small disappointment.
Nicky said: "I was hoping I might get a Blue Peter badge but despite dropping heavy hints to the producer, I didn't get one."
However she did leave with two "large lumps of glass" which now adorn her mantelpiece.
Feather Boy has been translated into 16 languages and talks are also under way about a television deal.
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