Ms Joss said she had met up the her new boyfriend shortly before the incident and had gone into The White Company to return something.
She said: "I was at the till returning an item.
"Tony was looking at some towels. While I was at the till I heard some shouting, some swearing and when I turned around to my right I saw Gareth."
Prosecutor Gareth Hendersn-Moore asked: "What was Gareth doing?"
She replied: "He walked behind me.
"He was heading in to the corner where Tony was, shouting and swearing. He was clearly very angry.
"I went to the till and ran to where they both were and I got in the middle of Tony and Gareth.
"I had my back to Tony as I was looking at Gareth.
"Gareth was shouting over the top of me. Words to the effect he was going to kill Tony
"Something along the lines of 'I knew you were after her'.
"I can't remember what he was saying but words to that effect."
The prosecutor asked: "How did the incident end?"
Ms Joss replied: "I was in between them. I tried to usher Gareth out of the shop. I pushed him to the top of the stairs.
"He was still shouting over the top of me."
Ms Joss continued: "We were stood outside of the main doors. At that point he said it wasn't over and he was going to break his legs.
"He was clearly angry and saying other things I can't recall but it got the attention of the security staff."
During cross-examination, Mr Field asked: "You clouted Mr Senior at the top of the stairs didn't you?"
She replied: "I did yes."
The solicitor then asked: "Whatever took place in the corner of the store between Mr Senior and Mr Dorigo, you were still speaking to the shop assistant and it happened so quickly you did not see what happened?"
Ms Joss replied: "Correct".