He passed the car, which he estimated was travelling about 70km/h, as he approached the sweeping bend and said he couldn't believe his eyes.
"My first comment was how did they do it? Have they driven all the way through the tunnel from Maioro Street or have they lost control on the bend? I was totally confused."
He called 111 immediately and was told dispatchers were following the car on camera.
"I was literally on that bend. There was a car on the inside of me and I think we just looked at each other and went, 'Wow'."
There was no indication to motorists that something was amiss.
"I didn't hear any tooting, no nothing further on the motorway and that's why there are so many questions for me. Why did they end up going that way and where did they end up? "
McGhie said he was glad he made it to work in one piece: " I do hope the other motorists avoided this idiot."
A Police media spokesperson said they received a handful of calls about a car driving the wrong way just after the tunnel entrance.
A very short time after these calls were made, the car was observed turning around and exiting the motorway, the spokesperson said.