Iain O'Brien lauds James Anderson's durability as a Test fast bowler but says that consideration will have to be given to the amount of overs he bowls (3:33)

Lancashire coach Ashley Giles believes James Anderson has lifted himself into the "realms of immortality" within English cricket after overtaking Ian Botham to be the leading Test wicket-taker.

Giles' comments were made before Anderson's match-winning display on the final morning in Grenada, a performance which certainly added weight to the view. Anderson propelled England to victory with a morning spell that will go down as one of the best of his career - eight overs, 3 for 16 on a docile surface - during a session where he had a hand in all six wickets to fall as he also grabbed two catches and conjured a superbly opportunistic run out of Jason Holder.

His performance in the Test, where he finished with overall figures of 6 for 90 from 46 overs, lifted him to joint second in the ICC rankings - a career high - alongside Ryan Harris. It came a week after he had become England's leading Test wicket-taker in Antigua, overtaking Botham's tally of 383, and he is now closing on 400 scalps.

Giles was part of the England team when Anderson made his debut against Zimbabwe, at Lord's, in 2003 where he took a five-wicket haul and while he said it was impossible to predict how successful his career would become, Giles knew there was a bowler with outstanding ability.

"He had a carefree nature about the way he bowled. I'm sure he did know where it was going but he just ran in and just let go," Giles told ESPNcricinfo. "It got down there, and over time he has developed that craft into something pretty special. There are those dark times, people saying you're past it and should be dropped, then he becomes a record-breaker and moves into the realms of immortality within English cricket."

While Giles sees Anderson continuing to lead the England attack for considerable time to come, he also thinks that one of his key roles now is to help nurture the new generation of pacemen who will, eventually, have to fend for themselves. Giles said he was surprised that Anderson had never held an official leadership position with the team given the wealth of knowledge he has to pass on.

"He would have moments when he was quiet, but always offered help and is always there for young bowlers in the team," Giles said. "In some respects I'm a little surprised he's not held some form of leadership position. He's been part of leadership groups but he has a heck of a lot of knowledge and value for the team.

Ashley Giles signs a flag to mark James Anderson's record wicket haul Slazenger

"Captaincy is difficult as a bowler, but even a vice-captain's position series by series, I'm surprised he's not held that. You need leaders of your bowling attack because that bowling attack is so important to win you games of cricket. Jimmy plays a big role in that."

The debate now centres on how to prolong Anderson's international career, although his performance in Grenada showed he could still push himself when the moment called for it - something Giles had presciently talked about when comparing him to how bowlers such as Courtney Walsh, Glenn McGrath and Shaun Pollock replaced pace with guile as their careers progressed.

"You still have your moments when you can bowl quicker to have an impact, but you get wiser and use your skills better," Giles said. "There has been careful management of him but there is just so much cricket and so much at stake. You want your best team on the field. It will be difficult, but it will be down to Jimmy how much more he plays."