Robert Sewell, 32, who split up with his partner just seven days earlier, kept a key to her home and broke in during the early hours of the morning.
Stuart Lody, prosecuting, said that his ex-partner had already formed a new relationship with another man, and the couple went out for dinner together before returning to her property in Tattershall.
Mr Lody said: “As they arrived and parked up the defendant was seen to be lurking around. They went in, locked the door and called the police.
“The police attended and gave them some advice about safety and left.
“Shortly after that the defendant suddenly appeared inside the premises.
“He came into the kitchen and approached (his ex’s new partner), punching him in the face.
“He shouted abuse at his ex-partner before picking up an item and throwing it against a hot tub, causing damage.
“The defendant then ran out. They locked the doors and called the police. Officers attended and again left.
“Just after 4 am there was a further incident. (Sewell’s ex and her new partner) were in the bedroom when the defendant suddenly appeared holding an empty whisky bottle which he threw against a wall, causing it to smash.
“He began arguing with (his ex) and calling her names. He then seized (his ex’s new partner’s) mobile phone and smashed it.”
Sewell’s ex’s new partner chased Sewell out of the house, but the defendant stole his wallet.
His credit cards were later used to buy hoodies at local shops.
The couple later discovered that both of their cars had been vandalised.
Sewell, formerly of Tattershall but now living at Hickford Hill, Belchamp St Paul, Essex, admitted burglary and common assault to his ex and her new partner. He also admitted four charges of damaging property and two charges of fraud by using his ex’s new partner’s bank card to buy goods at Tattershall Post Office and the Martin McColls store in Coningsby.
He was jailed for two years and given a five year restraining order banning him from contacting the pair, and from entering Tattershall.
Judge Simon Hirst, passing sentence, told him: “People who break into other people’s homes in the middle of the night, threaten them and use violence go to custody.”
Terry Boston, in mitigation, said: “He and (his ex girlfriend) had been living together for two years. He was a very angry man when he was confronted with what he was confronted with. He over-reacted to something that must have been very emotionally traumatic to him.
“He used the keys he still had from living there. He hadn’t handed the keys over. I don’t think he believed that the relationship had ended.”
Mr Boston said that Sewell has since moved to Essex and is running a business restoring listed buildings.