Alastair Cook defended the attitude of James Anderson and insisted the bowler has no need to change his on-field approach.

Barely a couple of hours after it was confirmed by ICC chief executive Dave Richardson that there would be no further investigation into the alleged incident between Anderson and Ravi Jadeja at Trent Bridge, the England captain reiterated the view that the man he rates as the "best English bowler" he has seen, requires an aggressive on-pitch persona to render him effective at the highest level.

But, after Richardson suggested there was "no place in the game for the use of offensive language," Cook suggested that, as long as the aggressive behaviour was left on the pitch, it should not be seen as a problem.

"We know that every time you pull on the shirt as an England player, or any international side, you are role models for anyone watching," Cook said. "We're all aware of that. We also want to play competitive cricket. We don't want to be too nicey-nicey with everyone saying they're playing in the right spirit. There's always that muddied line.

"We want to play competitive cricket like these three games have been played and I don't think we need to change too much."

Suggesting that Anderson had something of a "split personality," Cook explained that's Anderson on- and off-field personalities were as different as any player he had known.

"I've been round for dinner with Jimmy and he doesn't use that language with mum and dad," Cook said. "It's the same as a rugby player. You need to get yourself in the right frame of mind. I'm not sure every rugby player walks down the street wanting to tackle every person he sees. But you have to get yourself in that right mental state for you personally to perform. That's when it's important and that's why he has that slightly split personality."

The difference is that while tackling is a necessity in rugby, swearing is certainly not in cricket. But while Cook admits there may have been moments when Anderson has "overstepped the mark," he is reluctant to ask his key bowler to alter a method that has, on the whole, worked well for him.

"Of course there may have been little bits where he might have overstepped the mark throughout his career," Cook admitted. "But you'd rather be on that line than too passive. He needs that for his bowling and the way he bowled, especially at Southampton, was incredible.

"He is the best English bowler I have seen by quite considerable margins. He's not blessed with absolutely express pace, so to be able to control that ball and find a method like he did in Australia in 2010, where it didn't swing that much, is outstanding.

"I've probably not played with someone who changes so much when they get on to the pitch. But Jimmy is an experienced cricketer and he has found a method that he needs and he has become England's second leading wicket-taker in Test cricket. I'm pretty sure he'll be England's leading wicket-taker very soon and that's an outstanding achievement. He's found his way of doing it.

"Yes, he has a very different personality when he crosses the line. And I don't think anyone should moan about it because what happens on the field should stay on the field and off the field you should be a nice guy.

"Of course, you understand the parameters you have to play within, but I think the way both sides have played this series has been fantastic, apart from that one incident which has been blown up. I thought both sides have been very competitive and played it in the right way and in the right spirit."