A man who mugged a police officer's son and then falsely claimed the teenager sold him drugs has been jailed for five years.
Lincoln Crown Court heard how 23-year-old Peter Done had been released early from a three-and-a-half year sentence for attempted robbery.
The court heard how Done forced Robert McGibbon, 18, into an alleyway near the Royal Oak Pub in Grantham town centre on 19 November last year and robbed him.
Following his arrest he falsely claimed he was sold drugs by Mr McGibbon, whose father lectures on the dangers of drugs in local schools.
After a jury found him guilty on Tuesday, the court heard Done was on licence for a jail term imposed for an attempted robbery on a mobile grocer using an imitation firearm.
Done, of Trent Road in Grantham, was ordered to serve the remaining 306 days from his earlier sentence before beginning the new five year term.