Gamblers spent thousands of pounds on a Blackpool hoopla stall - unaware the odds of winning were 2,600 to one.
Trading standards officers seized equipment from the stand on the Golden Mile following public complaints.
And when a Lancaster University maths expert recreated the game he found the size of the hoop and angle of the peg made it practically impossible to win.
Dr David Lucy's experiment led to a successful prosecution of two men who admitted breaching gambling laws.
Trading Standards stepped in after officers secretly filmed two girls, aged 14 and 15, paying £3 for five attempts at the game.
Within eight minutes they had spent £70 - and won nothing.
Items from the stall were later seized and passed to mathematics expert Dr Lucy, who often helps evaluate forensic evidence for the police.
He recreated the game in laboratory conditions and invited staff and students to play - all without success.
Dr Lucy said: "What we found is that you could place the hoop over the pegs but throwing it into the air from two metres it would have to land precisely.
The pegs were cut at such an angle that the trajectory the hoop needed to take just would not work.
"We made nearly 600 throws without any joy which led to me calculating on the geometry that one would have to try 2,600 times to stand a reasonable chance of being successful."
His evidence was used as the basis for Blackpool Council to take stall owner Philip Williams, 53, and his assistant Darren Casey, 36, both of Blackpool, to court.
They were ordered by Blackpool magistrates to perform unpaid work for the community and Williams was also handed a 14-week suspended jail sentence.
Officials from Blackpool Council visited the stall over a two-year period and never witnessed anyone winning.
Most of the victims were visitors and young, vulnerable or elderly, the authority said.
Council public protection officer Shaun McKinney said: "One individual who had come to Blackpool had spent £1,200 to £1,500 playing the hoopla game.
"Obviously a lot of it was to try and win their money back from the initial losses, and it's a case of keep playing until they think they can win it back."