James Longworth

Admission: Banker James Longworth leaves court on Monday. Photo: AAP

Moments after an investment banker was refused entry into a Sydney bar, CCTV footage shows him turning back to the bouncer and punching him.

James Longworth, 33, went to Bar 333 on George Street in the CBD in September last year but was denied entry by the bouncer Fady Taiba.

In footage shown to the Downing Centre Local Court on Monday, Longworth could be seen walking away from Mr Taiba before turning back and punching the security guard.

One witness said Mr Taiba ''fell like a tree'' after the blow to the head. Another told police: ''He looked as though he was knocked down because he didn't put his arms out to try and stop his fall.''

Mr Taiba, then 43, was in a coma after the attack and had emergency surgery.

Mr Longworth's barrister Hament Dhanji said his client admitted punching Mr Taiba but denied intending to cause grievous bodily harm. His guilty plea to assault occasioning actual bodily harm was not accepted by the prosecution.

Mr Dhanji said Mr Longworth had no criminal history and was significantly intoxicated at the time. The UBS banker told police after the attack that he never intended to hurt Mr Taiba.

His barrister sought to question a number of civilian witnesses at Longworth's committal hearing about the force of Longworth's punch and whether it rendered the security guard unconscious before his head hit the ground, arguing Mr Taiba was ''standing on a raised platform or step before falling''.

But Magistrate Carolyn Huntsman dismissed his application saying that their accounts were largely consistent and there was no need for them to give evidence at the October 3 hearing.

Mr Longworth was granted bail last year after his family offered to post more than $500,000 surety.

AAP