This sequence of events is refuted by Mortimer, who says that a friend of his also present in the VIP section of the club, in fact introduced him to Pistorius, who he claims was "drunk" and "very aggressive."
The 27-year-old Paralympian is currently on trial for the murder of his girlfriend Reeva Steenkamp, who he claims he shot after believing her to be an intruder.
The trial has been adjourned until 8 August when closing statements and arguments will take place, before the judge, Thokozile Masipa, considers her verdict.
Mortimer said of Saturday night: "Oscar knew one of my friends and said, 'Oh, you are the infamous Jared Mortimer.' He immediately started talking about his friends and how they had backstabbed him.
"He then mentioned one of my friends and claimed he had a lot of dirt on that person."
Things at this point turned slightly for the worse, Mr Mortimer claims, with Pistorius "going on about how influential his family is and how connected they are.
"He even pulled out his phone to show me pictures of armoured cars. He said 'My family owns SANDF. Zuma works for us. I'll piss on Zuma'."
Pistorius then poked him on the chest, Jared claims, pulling his neck to talk to him.
"He said 'you'll never get the better of me. I'll always get the better of you'," Mortimer alleges, before he then pushed Pistorius, who fell. Bouncers then arrived to neutralise the situation and Oscar left the club, he said.
If found guilty of premeditated murder, Pistorius faces at least 25 years in jail. He denies the charge.
Pistorius then broke a five-month Twitter silence on Sunday and Monday, sending out four Tweets one of which was a collage of the athlete with young amputees with the message: "You have the ability to make a difference in someone's life."
- UK Independent