Britain's Danny Williams knows exactly why he was hand chosen as Mike Tyson's opponent for their heavyweight bout later this month.

"I've got a good record, I'm big, I look the part... and they think I'm going to be knocked out quickly," said Williams in a teleconference on Tuesday to promote the July 30 fight in Louisville, Kentucky.

With Tyson climbing back into the ring for the first time in 17 months, Williams (31-3, 26 KOs) is seen as nothing more than the first installment on the former-undisputed champion's massive $40 million debt.

But the WBU (World Boxing Union) and British heavyweight champion has other plans.

A journeyman fighter virtually unknown outside of his hometown of London, Williams is relishing his underdog status but refuses to under-estimate Tyson's declining skills.

"It's a known fact Tyson isn't what he use to be but even though he's 40 percent of what he use to be he's still a world class fighter," said Williams. "He's still one of the best heavyweights out there so I still think it's a massive achievement for anyone to beat him.

"His 40 percent is still better than most fighter's 100 percent.

"He's still a world class fighter and still has world class punching power.

"On any given day he can definitely still win a world title but he has to get through me and I don't think he will."

Williams has set up training camp in New York city where he is getting quality sparring that was unavailable to him in England.

As part of his preparations Williams will spar with Clifford Etienne, Tyson's last opponent who he knocked out in just 39 seconds of the first round.

"I think he (Etienne) can tell me about the intimidation factor," said Williams. "I don't think he can tell me much about Tyson's technique he wasn't in there long.

"When I came to America a lot of people thought I was just another English bum but they've been surprised.

"I've been constantly stopping my sparring partners and knocking them out.

"People have been surprised by my speed and power and that an Englishman can fight like that."