Paul Pluck, 44, of Eagle Way, Hampton Vale, Peterborough has been found guilty of two counts of indecent assault on a girl under the age of 14 at a trial at Cambridge Crown Court.
The court heard that Pluck was about 17-years-old and babysitting the five-year-old victim when the offences occurred in the late 1980s in Wisbech.
Pluck was jailed for four years and six months for each count to be served concurrently.
Det Con Leanne Malinowski said: 'The victim has shown great courage taking the brave step of speaking out. I hope that the guilty verdict and sentence given to Pluck will help her move forward with her life.
Pluck was found not guilty of two further charges of indecent assault on a girl under the age of 14 years.
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