Lomu has played two games for Cardiff Blues after returning to rugby following a kidney transplant in July 2004 and now he is training with Campbell - part of the victorious Great Britain 4x100 metres squad at the Athens Games - and his coach, former Olympic and world champion Linford Christie.
The former All Black winger has spent almost three years away from the sport due to health problems but now he is attempting to work his way back to full fitness and Campbell insists he can soon make the difference.
Campbell told the BBC: "If he wants to be quicker, I'll get him quicker. He'll feel the difference in two weeks.
"It's great to be working with one of the world's greatest sporting icons."
Campbell also believes Lomu can achieve his ambition of returning to the international scene with the 30-year-old setting his sights on the 2007 World Cup.
"He's still got that aura," said Campbell. "He's still got that fear about him.
"He's not the type to beat himself up because he is not 100 per cent yet.
"He's extremely realistic. To me, he has already fought the biggest battle and that is 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.
"But let's not forget, this (lay-off) was extremely serious. The fact he is even running again is totally amazing."
Lomu's career seemed to be unstoppable before it was derailed by a kidney condition called nephrotic syndrome.
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 - and Campbell insists it is about re-educating his body.
"He won't beat me over 100m. 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 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.
"I'm confident I can do it. He'll be back and he'll be back in a big way."