He was just a baby-faced eight-year-old when he first burst into song on the back seat of his parents' car as they drove him to primary school, mimicking Whitney Houston singing My Love Is Your Love.
Stunned by the sultry soulful sound that came from their son, Fred and Kate Smith were certain he had something special.
Before long they had found him a singing teacher, encouraged his love of music and, perhaps most importantly, didn't laugh when he told them that, one day, he wanted to be famous.
That day arrived at a star-studded ceremony on Sunday in Los Angeles when Sam Smith scooped not one but four Grammy awards – best new artist, record of the year, song of the year and best pop vocal album.
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Sam Smith scooped not one but four Grammy awards – best new artist, record of the year, song of the year and best pop vocal album, pictured with Taylor Swift
And the audience were touched when the first people he thanked were his mother, father and sisters Lily, 19 and Mabel, 18, who were all there. He held up his award on stage and said: 'Mum and Dad, Lily and Mabel, I've won a Grammy!'
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ShareTo be honoured four-fold would be remarkable for the most established of stars, but for a 22-year-old singer-songwriter from Cambridge, who until recently was making ends meet by cleaning toilets, it is astonishing.
His banker mother Kate Cassidy (pictured) was sacked after being accused of spending company time promoting his pop career
Those who saw Smith being congratulated by the likes of Sir Paul McCartney could be forgiven for thinking his rise has been meteoric.
But his path to success has been well planned by both Smith and the parents who have supported him through every high and low.
Both – especially his mother – sacrificed so much to ensure their son had everything he needed to turn his talent into a successful career.
In 2008, when he was 16, his City banker mother was sacked for gross misconduct from bonds and currency brokerage Tullett Prebon after being accused of spending company time promoting his pop career.
Mrs Smith, known professionally as Kate Cassidy, started a High Court battle against the firm to recover £401,643 in salary, £900,000 in annual bonuses and £350,000 in share options.
The outcome was never published but reports suggested she was awarded £800,000 compensation which, a relative has claimed, she later used to help set her son up in London closer to record producers.
Smith himself is adamant that the claim against her was unfounded and she never had time to devote to his fledgling career. 'My dad, bless him, is the one who should get credit for that,' he said last year. 'Every day after school he would drive me to Kilburn where I'd be recording in studios.'
A year ago many had not heard of Smith, but then suddenly his songs were being played everywhere. By the end of the year he was the only solo artist to have sold more than a million albums in both the UK and the US, with his debut In The Lonely Hour.
Few can have failed to hear his melancholic falsetto voice on emotionally charged hits such as Stay With Me and Money On My Mind.
Yesterday the singing teacher who coached him for ten years from the age of nine praised him and his parents, saying: 'He just blew me away from the word go.'
Joanna Eden added: 'He impressed me with his hard work and belief and courage. I felt I was witnessing something incredible. He is an example of what you can do if you believe in yourself.'
Smith was born in 1992 to parents who were, without question, fiercely ambitious. His 54-year-old father is an ex-van driver who once ran a fruit and veg stall and who largely stayed at home with his children. His 50-year-old mother began as a bank clerk for Barclays but went on to become a highly paid City bond dealer.
They had a tiny two-bedroom Victorian terrace cottage in the village of Linton but his mother's eventual £200,00-a-year salary saw the family upgrade to a stunning £500,000 18th century Grade II-listed house in Great Chishill.
Devoted dad: Sam pictured as a boy with his father, who drove him to recording studios in Kilburn every day after school while he was growing up
Performer: A young Sam poses smiling broadly in a Buzz Lightyear costume
Smith paints a picture of himself as a tortured young soul, spending his after-school hours singing along to tracks by idols such as Luther Vandross and Aretha Franklin.
By the age of 12 his mother was wheeling him out at parties to sing for her guests, and by 14 he was starting to attract attention from prospective managers.
But empty promises of stardom from music industry people proved damaging to his young ego. He recently recalled how he would regularly be told: 'You're going to be famous by next year.'
'They'd tell me things and I'd go to school the next day and I'd be like, 'I'm going to be doing this in a few months. I'm going to be singing a song with this person'. It never materialized and I looked like a complete idiot.'
Sam Smith puts an arm around his mother as he pays tribute to his parents for his success
At home as well he was learning just how precarious life could be. He was 16 when his mother was sacked by Tullett Prebon in 2008 – a reminder that success, even when it comes, can be ephemeral.
He recalled: 'The climb to money was sudden. We were doing nicer things, building, travelling around the world. But just as quick was the decline. We were in a whole different situation.'
At 18 his parents separated and Smith headed to London where it seemed he would never find the recognition he was searching for.
He wrote a self-pitying song called Little Sailor, about a young man who dreamed of a career in music and was getting nowhere. 'I was basically saying, 'I give myself one more year to do this, then I give up'. My friends were at university and travelling and I was stuck in London cleaning toilets and I'd already had six managers.'
Members of the audience were touched when the first people he thanked were his mother, father and sisters, pictured with Rihanna
Those who saw Smith being congratulated by the likes of Sir Paul McCartney could be forgiven for thinking his rise has been meteoric
It was manager number seven, singer-songwriter Elvin Smith, who is credited with turning Smith's career around. He teamed him up with songwriter Jimmy Napes and they began writing together.
But it was, he claims, his experiences of unrequited love which inspired the music which transformed his career. Smith, who is openly gay, says pain is a more powerful emotion than happiness.
At the Grammy awards he thanked the man who inspired his album, a man he fell in love with last year but who never loved him back. 'Thank you so much for breaking my heart because you got me four Grammys,' he said.
More recently, he had a short-lived relationship with 23-year-old New York model Jonathan Zeizel.
Despite all his talk of heartache, Smith was clearly overjoyed at his success, telling his millions of Twitter followers that Sunday was the 'best night of my entire life'.
Plenty to celebrate! Sam was spotted out and about in Venice Beach on Monday evening as he headed out for dinner at The Tasting Room with a friend
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