A man head-butted his then partner in a supermarket after she commented he was using cocaine.
CCTV footage was played to Thomas Page by his lawyer Anita Toal, who said he had little or no recollection of the attack.
Mrs Toal told magistrates: “He could not believe it was him.”
Page (24), of Burton Road, Spalding, admitted assaulting Debra Trevey at Sainsbury’s on May 25.
Magistrates on Thursday adjourned sentence to July 4 for a report and extended Page’s bail.
Prosecutor Marie Stace said Ms Trevey walked towards the Spalding store toilets but, after her comment about cocaine, Page stood in front of her to block her path, hit her face with a shopping bag in his hand and head-butted her.