Benjamin Tuffnell, 46, was approached by officers while sitting in his car with the lights and engine off about 11.30pm on July 17.

He had drunk three beers and two wines at a Tourism SA function, then drove a colleague to her car in the lead-up to the CBD incident.

Adelaide Magistrates Court heard on Thursday he was belligerent, disrespectful and became physical with police before a cage car was called and he spent more than two hours in custody.

A breath test returned a blood alcohol content reading of 0.097, though he said he did not feel intoxicated.

The father-of-two was corporate affairs director at Tourism SA at the time of his arrest, but was dismissed after failing to tell his employer about some of the charges.

Before that, he worked as general manager of corporate affairs at the Motor Accident Commission from 2007 until 2014.

Tuffnell pleaded guilty to drink driving, failing to comply with a direction to leave his vehicle and resisting police, while two counts of assaulting police were dropped.

Chief Magistrate Mary-Louise Hribal handed him a conviction, fine and six-month licence disqualification for drink driving, but did not record a conviction for resisting police or failing to comply.

She said Tuffnell, who was now working two days a week as a consultant, would find it difficult to land work at a similar level to before his dismissal.

The chief magistrate said his actions were out of character.

"Whilst your behaviour on this night was extremely poor, there is no doubt that your actions in relation to the failure to comply ... don't represent the man who, for the last 40-odd years, has led an otherwise blameless life," she said.

For all three offences she fined him a total of more than $3000.

Tuffnell made no comment to reporters as he left court.

Australian Associated Press