Little did he know that later in the day details of the four- decades-old romantic rendezvous would become public knowledge.
For the first object of Mr Smerdon's boyhood desire grew up to become Cherie Blair, the outspoken wife of the Prime Minister, who yesterday revealed to the world the details of her magical moment with him, under a railway bridge in Liverpool.
Long before she fell for a long-haired, guitar-playing Tony Blair while they were training to be barristers, Mrs Blair had her first romantic encounter with a chubby-cheeked boy in knee-length shorts and slicked back hair.
She revealed details of the clinch at a stall set up by the Ordnance Survey, which produced a map of her childhood home in Ferndale Road, on her request. The stall was part of a series of stands at the Labour conference in Brighton.
Pointing to the spot the embrace took place at the local park, she spoke of the tryst that led to her first romantic experience. "Under the railway bridge was the first time I was ever kissed, at the age of seven ... by a boy called Stephen Smerdon," she said.
Mr Smerdon, 50, said he was "just glad that Cherie remembered me". He said he felt "nostalgic" when she described the occasion, that he will "never forget".
"We used to live in the same street," he said. "She was a lovely girl. We were too young to have a big romance, but I don't care what anybody says nowadays, she is a caring person and is very nice."
Mr Smerdon, who has been married to Claire for 13 years, lost touch with Mrs Blair when he left Liverpool to join the Navy. Today he runs the Bull Inn pub in Whitwell, Hertfordshire, and often regales customers with the tale of the kiss.
Now a distinguished, silver-haired resident of the quiet village near Luton, he was pictured at the age of seven looking cherubic in shorts, a tie and a smart V-neck jumper.
Mr Smerdon's father, Denis, was a teacher who taught Cherie at St Edmunds and St Thomas primary school in Merseyside.
Mrs Blair's parents had just split up when Denis Smerdon, who lived in the same street as Mrs Blair's mother, suggested that she move up a year at school.
Mrs Blair never forgot the influence the schoolteacher had on her life. Although he died in 2001, she invited his widow, Molly, to Downing Street, after Labour's general election victory of 1997. Last year, she posthumously nominated him for a project that recognised his achievements and called him an inspiration. She described him as having "a huge influence in my life" and said he had been a "good man and a wonderful musician who gave inspiration and belief to many people including myself".