Wladimir Klitschko (left) of Ukraine and Tyson Fury of Britain Photo: IC

Tyson Fury faces the acid test of his boasts that he will end Wladimir Klitschko's four-year reign as undisputed world heavyweight champion when the pair clash in Duesseldorf on Saturday.

The 27-year-old English challenger is undefeated in his 24 fights with 18 knockouts as he faces the vastly more experienced champion, 12 years his senior, who holds the WBA, IBF, IBO and WBO belts.

Fury has much to prove at Duesseldorf's Esprit Arena, having insisted he has spotted "chinks" in Klitschko's amour and has promised to "expose" him in the ring.

"Old guy, young guy. Old champion, new champion. Enough said," was Fury's succinct appraisal.

Klitschko, 39, suffered the last of his three defeats more than a decade ago and plans to make Fury the 54th knockout and 65th win of his career.

As he rightly points out, "Fury has never faced an opponent like me before.

"First I destroy my opponent mentally, then physically."

Klitschko made a point of shaking hands with Fury before their news conference in Duesseldorf and has mainly soaked up the Briton's taunts.

He's heard most of them before.

Britain's David Haye insisted he was going to knock out "the large, slow robot from the Ukraine" in July 2011, only to lose unanimously on points.

The victory gave Klitschko the WBA belt to make him undisputed heavyweight champion and only the WBC title, held by Deontay Wilder of the US, is not in his collection.

In September, Fury showed his theatrical side by bursting into their London news conference dressed as Batman.

He pretended to knock out a character dressed as the Joker, before telling Klitschko "This is a fool ... just like you."

The champion, nicknamed Dr Steelhammer, sees Fury as "a clown" with a "few screws loose" who needs "therapy," which the Ukrainian plans to administer in the ring.

Fury did little to help his cause by giving a bizarre interview to a British newspaper earlier this month when he said the end of the world is approaching.

The British fighter expressed some extreme opinions on homosexuality, abortion and paedophilia.

"He was actually a funny guy, an entertainer, at the start," Klitschko told German magazine Sport Bild this week. "But what he has been saying recently is embarrassing and moronic."

Fury has even serenaded Klitschko during an open training session in Duesseldorf.

He adapted the Bette Midler song "Wind Beneath my Wings" to include the lyrics "I'll be the one with all the belts" come Saturday night.

The Briton says he will seek out veteran crooner Rod Stewart, who is ­providing the pre-fight entertainment, for a duet in the ring if he wins.

But Klitschko expects Fury to sing a different tune come Saturday night.

The original fight date in October was postponed due to Klitschko's calf injury which has now healed.

The champion looks in good shape, even though he will be giving away more than a decade in age and a few inches in height.

Former heavyweight champion Lennox Lewis has tipped Klitschko to knock Fury out in the fifth round.

Five of his eight fights since beating Haye have been won by a knockout of some description.