RORY Arnold’s recall beside Adam Coleman has created the twin peaks of world rugby with the tallest locks pairing in Wallabies history.

Coach Michael Cheika has fearlessly united his loftiest yet most inexperienced locks to rumble with Argentina at Twickenham.

The experiment on Sunday morning is the boldest move yet in Cheika’s master plan to broaden the pool of Test-toughened talent.

Cheika will be far more focused on their energetic output than the bare numbers that define the 2.08m Arnold (four Tests) and his 2.04m offsider Coleman (five).

It’s part audition too with the All Blacks and their supreme pairing of Sam Whitlock (80) and Brodie Retallick (55) lying in wait in Auckland for October 22.

Wallabies tall timber Rory Arnold (left) and Adam Coleman will take on Argentina at Twickenham. Source: News Corp Australia

A thorough test of Australia’s two lock debutants of the past four months against a brawny Pumas pack is a world class challenge in itself.

“We can’t be frightened to do that no matter what game it is, whether it’s Argentina or New Zealand,” Cheika said.

“We’ve got to understand that to broaden the base of players and the quality, we need to be working with these guys more regularly.”

That applies equally to 125kg Lopeti Timani, whose imposing physical presence at training has won him the No. 8 job for the first time.

“With the profile of our other forwards, with more jumping-style No. 6s, that ball-carrying, Wycliff Palu-style No. 8 is something we want to have as well,” Cheika said.

Leroy Houston is still a big shot at a Test debut off the bench, with his back-of-scrum expertise, when it is finalised later today.

Prop Allan Alaalatoa, now his knee is sturdy again, is pressing Tom Robertson for a bench spot.

Arnold ran out of steam after 30 minutes when he was blooded against England in June.

It’s not surprising when you consider the ACT Brumbies forward’s ascent from fun footy with the Bananas, the Gentlemen of Murwillumbah, just four years ago.

It’s not just Arnold but the whole Wallabies outfit that is far fitter than June to play the up-tempo, attacking style to sting the Pumas.

“We’ve got (Rob) Simmons and (Kane) Douglas as locks with lots of experience and getting guys in there to challenge them is the way we’ve got to broaden the base,” Cheika said.

“All of a sudden you’re going to have five or six (locks) you can choose from.”

Judges perplexed at Cheika picking his seventh lock pairing in eight Tests need to understand that the changes are aimed at that bigger picture but hopefully with fewer teething problems at Twickenham.

“Rory’s just been aggressive, his lineout jumping has really improved and so has his mobility and ball-carrying,” Cheika said.

“He got into rugby late so he’s maturing and this is a real opportunity for him, and other guys, to say, ‘I’m a starter’.”

Most recently, Andries Bekker (2.08m) and Eben Etzebeth (2.04m) matched the Aussie lock pairing for height in the 2012 South African second-row.

“Coleman has moved on nicely in his position, calling lineouts and stuff like that,” Cheika said.

It’s remarkable how the code has moved on from Argentina’s first Test in Australia at Ballymore in 1983. The Wallabies played a 1.86m lock that day in Duncan Hall.

WALLABIES: Israel Folau, Dane Haylett-Petty, Samu Kerevi, Bernard Foley, Reece Hodge, Quade Cooper, Will Genia, Lopeti Timani, Michael Hooper, Dean Mumm, Rory Arnold, Adam Coleman, Sekope Kepu, Stephen Moore (c), Scott Sio. Reserves: (to be announced).

RUGBY’S TALL TIMBER … LOCK PAIRINGS AROUND THE WORLD

Australia: Rory Arnold (2.08m)-Adam Coleman (2.04m)

South Africa: Lood de Jager (2.05m)-Eben Etzebeth (2.04m)

New Zealand: Brodie Retallick (2.04m)-Sam Whitelock (2.03m)

England: George Kruis (1.98m)-Maro Itoje (1.95m)