"LIKE a switch" a Hayle man had turned into an attacker, strangling his fiancée and biting her twice on the chest, Truro magistrates were told.
Samuel Paul Thomas then tried to hug Keely Waller and then left the caravan they were in. The following morning he behaved as though nothing had happened.
Thomas, 21, of Tamarisk, Hayle, pleaded guilty to assaulting Miss Waller at Penzance on January 20.
Anita Kennett, for the prosecution, said the couple were engaged to be married, having been in a relationship for four years. She loved him and wanted him to return to her.
On January 20, fed up with waiting for him to go into town with her, she said she would go on her own. "Like a switch" he started to attack her.
He grabbed her by the shoulders and threw her backwards, causing a scratch on her chest, and then began to strangle her, making it difficult for her to breathe. He let go, and then bit her twice on her right breast.
Elliott Moore, for the defence, said Thomas had health issues and the possibility of a learning disability.
The case was adjourned for a probation report.