DON’T ask Jim Zockoll if he’s going to retire.

“Nah!” says the tough American entrepreneur, waving away the idea like a bad smell. He’s got other plans. “Let me tell ya,” he continues. “I’ve spent years developing this concept called Phonenames . . .”

The idea is simple: you dial the company name using the letters on phone keypads. You’re straight through. It’s already big business in America and Zockoll has spent millions protecting the rights to it over here.

“But nobody’s listening!” he suddenly shouts, leaning across the meeting-room table.

“In America it’s been going 35 years. I don’t know why nobody’s buying it here! But for the next couple of years, that’s what I’m going to do.”

Zockoll, a big-nosed, silver-haired bear of a man, likes to talk in exclamation marks.

Part Irish, part German, but 100% American serial entrepreneur, he has made a fortune in Britain through Dyno-Rod, the drain-cleaning specialist he founded, but has never taken his eye off the next main chance.

This month he’s bringing Dyno-Rod, his “baby”, to the Alternative Investment Market and handing over control to a new team so he can turn his full attention to Phonenames, his last big project.

At 74, he has seen seven start-ups into bankruptcy and three into longevity, of which Dyno-Rod has been by far the most successful. Now he wants no distractions.

But at his age, why not take it easy? “Cos I’m hungry, desperate or greedy, I dunno,” he growls, and then grins.

He doesn’t need the money. The Dyno-Rod float, priced at £57m, will earn him and his family more than £40m. And he’ll be keeping a 10% stake in the new entity, as well as hanging around to offer advice if the new team needs it.

“You know what?” he says, suede tie unknotted halfway down his shirt, “I think they’re going to use me, suck me dry and then dump me, and that’s what they should do, ’cos I’m too entrepreneurial.

“I’m like a guy on crack, bouncin’ around. They’re steady, more professional — it’s what the business needs.”