American sprinter Justin Gatlin may be in excellent form and won the IAAF Diamond League final last month with a personal best of 9.77 in the 100 metres.

But his recent success on the track is understandably dividing opinion given his past doping offences - indeed he is running faster than ever despite being into his 30s.

When he was nominated in the IAAF Athlete of the Year awards, his inclusion led to uproar in many quarters.

So what does his form and continued presence mean for athletics?

We spoke to Derval O'Rourke and David Gillick to get their views on a thorny issue for the sport.

"It's very impressive," said Gillick of Gatlin's form, "but it makes you sick. As clean athletes we come up through all the ranks, you understand the sport and stay within the rules. And then you're sitting at home watching a guy tearing up the track.

"He's parading around like he's the king of the sport."

Derval also contrasted Gatlin's attitude to that of Dwayne Chambers who was also banned because of doping in his career.

"He's never shown any remorse for it. Even if he came back in, I wouldn't be the biggest fan of Dwayne Chambers but he came back, he admitted his use and he did as much as he could do to kind of try to make up for it."

Gatlin's agent has claimed that Gatlin's long lay-off due to his past doping ban as a reason why he is in such great form.

"He can talk about freshness but that doesn't make sense," said Derval, who spoke about a University of Oslo study which shows that there could be a long-lasting performance benefit to taking banned substances.