When the parking attendant spotted the copper pipes and wires snaking from beneath the VW Golf and through the window to a battery on the backseat, he decided to play it safe and call the police.

That call resulted in buildings near the parking cellar on Landgreven 2 near Kongens Nytorv in central Copenhagen being evacuated and police setting up a 50-meter perimeter around the car they feared may have been wired as a massive bomb that was primed to go off beneath government offices.

The rigging, it later turned out, wasn’t a bomb. It was a science experiment that Dan Zethraeus, a Swedish film director and amateur inventor, who currently works for Swedish national broadcaster SVT, had installed on his car to try and harness electricity.

“I’m really sorry that I caused so much trouble. I am really sorry,” Zethraeus told Jyllands-Posten newspaper. “I understand now that it could have been thought of as a bomb, but that was not at all my intention.”

Zethraeus explained that it took him some time to realise that it was his car which was the focus of the commotion yesterday morning.

“I was on my way to collect the car, but couldn’t get there because the streets were blocked so I sat down in a café. That’s when I was called by the Swedish press who told me my car was involved.”

He added: “I had to explain to the bomb disposal experts that the rigging was an invention I had started to try and save the environment by allowing the car to collect electricity directly from the road.”

He had decided to test the invention while on a two-day holiday in Denmark and left the rigging on the car after he parked it.

“The rigging is not illegal and the police did not ask me to remove it, but I don’t think I will be driving with it in Denmark any longer,” he said.

But while the international media were interested to know how the device worked, Zethraeus refused to reveal any details before he had a patent.