If we're all patient we will see the best of him and I hope he realises his dream and gets to play in the World Cup Darren Campbell

Lomu is training with Campbell and his coach Linford Christie in Cardiff in the hope of fast-tracking his return to fitness after almost three years out.

Campbell told BBC Sport: "If he wants to be quicker, I'll get him quicker. He'll feel the difference in two weeks.

"It's great to work with one of the world's greatest sporting icons."

Lomu, 30, is two games into his comeback with Cardiff Blues after having a kidney transplant in July 2004.

His ultimate aim is to return to the New Zealand squad in time for the 2007 World Cup in France.

Predicting the likelihood of such a remarkable return is far too premature, but Campbell certainly believes Lomu has the strength of character to get there.

"He's still got that aura, he's still got that fear about him," said Campbell, who won gold for Britain in the 4x100m relay at the 2004 Olympic Games and silver in the 200m four years earlier.

"He's not the type of person to beat himself up because he's not 100% fit yet. He's extremely realistic.

"To me, he's already fought the biggest battle and that's to even get back playing.

"Now that he's here, if we're all patient, we will see the best of him. I hope he realises his dream and gets to play in the World Cup.

"My gut feeling is he will. He says he can, so who am I to question what he can achieve? He's come back before.

"But let's not forget, this [lay-off] was extremely serious. The fact that he is even running again is totally amazing.

"So if he feels he's going to come back and make that World Cup team, who am I to argue?"

Lomu exploded onto the scene at the 1995 World Cup

Lomu's natural pace and towering physical frame made him almost impossible to stop before a debilitating kidney condition called nephrotic syndrome threatend to end his career.

At his peak, the 6ft 5in winger could run 100m in 11 seconds - just a second or so slower than the world's top sprinters.

Ten years on and a few pounds heavier, rugby fans worldwide are eagerly waiting to see if Lomu can get back to anywhere near his best.

Blues conditioning coach Trystan Bevan will take care of Lomu's general fitness work, leaving Campbell and 1992 Olympic 100m champion Christie to get him firing from the blocks.

It is all about getting Lomu's body to "remember" how to run fast, says Campbell. And he is confident he can get the results.

"He won't beat me over 100m," he joked. "But then saying that, I couldn't run past him with a rugby ball.

"I worked with the Wales rugby squad before the last World Cup. I know they thoroughly enjoyed the sessions I gave them, and felt they benefited from them.

"I know pretty much what I'm going to do with regard to Jonah. It's not going to be too difficult for him.

"After being out for a long time like he has, it's just about re-educating the muscles to remember how to do things at a faster pace.