There has been some backlash against those who filmed the incident, with several commentators claiming the couple's privacy had been breached, but Mr Edwards said it was unlikely the police could take action if a complaint was made.
"The people who were watching, we may criticise them for a lapse of decency in taking advantage of that, but it is unlikely there'd be any legal liability for their action," he said.
Marsh Ltd chief executive Grant Milne said the company was taking the incident "very seriously".
"Matters like these, we don't just brush over them. An investigation will take place and we'll take action from that investigation," he said.
"Behaviour like this we don't condone, and it's not the sort of thing we expect to see going on in our place of employment."
Employment law expert Blair Scotland said that the pair could lose their jobs over the incident.
Once the company had gathered all the information it could, the two employees would be invited to separate meetings where they could have legal representation and give their own version of events.
The key element, Mr Scotland said, was whether Marsh believed it, or its brand, had been brought into disrepute.
"A funky modern IT outfit might say, 'Don't do that on other people's desks please, otherwise don't worry about it,' and have no disciplinary action whatsoever. The nature of the employer can play a big part in the outcome," said Mr Scotland, partner at Dundas Street Employment Lawyers.
"It's not necessarily a done deal that they're out the door."
He said it was an "interesting" case, and one that will divide opinion. "Some people will have a bit of a snigger while others might wonder what sort of company allows these sorts of activities after hours. It's not an easy process for an employer to weigh up," he said.
The lawyer also doubted that those who took the photographs or videos and posted them online had broken any privacy laws.
"What's the different between doing it in a lit building with a pub across the road as opposed to doing it in a park?"
Yells of approval
Patrons of Carlton Bar and Eatery who witnessed the romp said they cheered the couple on. Even the band stopped playing to allow more than 50 pub-goers to take in the show.
"The entire bar united in cheering them on," said one witness on social network Reddit.
"It started with a casual flirt. Then the kiss, grabbing the attention of all. Get it, son! Finally they moved to the back of them room, thinking they were unseen. Off comes the tights, down goes his head. By this stage, 50 bar patrons were pressed up against the window yelling their approval.
"To be honest, after watching them f*** for a good half hour, people started to get bored and drift off back to the dancefloor."
The cheeky band then started again with Kings of Leon song, Sex on Fire.
Some people online are claiming that the man is in his 50s and married with teenage children. Others say the woman was his secretary and "recently engaged".
Witnesses claimed that the pair "celebrated" afterwards with a glass of wine.
"Funniest thing I have seen in a while. Made for a great night," said Ally Hills, who was in the Carlton on Friday night.
Alastair Neville said he was "fortunate enough to be at this historic event".
"I would say 99 per cent of the pub got behind this couple and cheered them on as s*** got out of control. The atmosphere was the most positive I've ever experienced at a bar!"
He posted the first photo of the encounter on his Facebook page at 10.59pm on Friday. Mr Neville then gave a real-time commentary of events.
Absolutely no idea
Leah Bates, 25, was up from Timaru catching up for a drink with a friend, her sister and her partner, when the "show" started.
On her way back from the toilet, she wondered why everyone was looking outside.
"We looked out the window and it was all go. Everyone in the whole place was watching," she said.
"They had absolutely no idea - it was brilliant. We went upstairs and watched from the balcony, and everyone was cheering -- especially when he dropped her on the floor - twice. Everyone just lost it.
"They turned and faced the window and everyone was cheering and waving but they obviously couldn't see us. It was pretty funny, a bit of a show for the night. Everyone was pretty impressed with how long he lasted. He went for ages."
Most pub patrons were using their phones to take photos or film the performance.
Ms Bates now says she feels sorry for the pair and hopes they don't lose their jobs. "They didn't look like a couple. It was way too passionate for that."
