What is really at stake at Twickenham on Saturday?

This tournament is what it is; one born out of necessity and circumstance, not prestige.

Just this once though, perhaps the result is not the main goal in the frantic blink-and-you'll-miss-it world of Test rugby.

For Andy Farrell's Ireland, this is a game about identity.

In his first year as head coach, Farrell has gone round the course in par. Winning the games he ought to be winning and losing the ones in which Ireland entered as underdogs.

Consequently, we have not learned a great deal about the direction this side will go under new management. Saturday's game has the potential to answer some of the most burning questions still unknown about Ireland.

One question that has hung over the Ireland squad for longer than Farrell has been in position is that of the succession plan at fly-half.

It would be unfair to accuse the IRFU, Farrell or former head coach Joe Schmidt of not planning for life after Johnny Sexton, but the fact remains that Ireland's first choice fly-half is now 35, and with each season that passes the lack of an obvious successor becomes increasingly problematic.

In the injured Sexton's absence, Ross Byrne is given the chance to steer the ship from 10 at Twickenham, where he will partner up with Jamison Gibson-Park, whose first start last weekend was dynamic enough to retain his place with Conor Murray forced to assume an unfamiliar substitute role.

There is significance here, for the first time since a 2011 World Cup warm-up game, Ireland play England without at least one of Sexton and Murray in the starting line-up.

If Byrne and Gibson-Park can conduct a composed and accurate Irish performance at the home of their chief tormentors over the last two years, that will go some way to reassuring fans of what the future holds.

'How will Byrne cope with the big occasion?'

For Dubliner Byrne, 25, shining in the same orbit as Sexton is not an unfamiliar task.

At Leinster, Byrne's role has evolved into something much more significant than Sexton's understudy. In the last four seasons he has played nearly twice as many minutes as his club and international captain.

This week Farrell offered the view that Byrne is a player for the big stage, a view shared by Leinster coaches and evidenced by the decision to start him in August's Pro14 final over a fully fit Sexton.

"How do you find out about how they cope with the big games, the big occasions unless you give them the chance?" Asked Farrell.

"We can't just give him the chance of picking him in the squad and just training the whole time.

"Obviously Ross has been involved in some big games for Leinster and this is his chance to go to Twickenham and be part of a great team performance as well."

A place in the pecking order up for grabs

Byrne's reputation for now is solid, if not spectacular.

At Leinster he sits nearly alongside Sexton at the top of pecking order, above stiff competition from younger brother Harry and Ciaran Frawley. But for Ireland, his place is far less assured.

Below Sexton, the international depth chart is muddied. In 2016 Joey Carbery began to emerge as the heir apparent.

It was with this in mind that the IRFU facilitated Carbery's move to Munster two years later, where the starting fly-half jersey would immediately be his and on that platform, it was hoped, he would stake a reasonable claim for the Ireland job.

Such was the belief in Carbery that he was taken to last year's World Cup, perhaps at the expense of a third scrum-half, despite carrying yet another injury.

Injury has plagued the desperately unlucky career of Carbery who, at 25, is still viewed by many as Ireland's best long term option, should his body allow him a return to form.

Jack Carty has, for now, fallen out of favour while Ulster's Billy Burns is yet to be awarded his first start.

It all makes for an unclear picture, and a door that is wide open for any of the aforementioned to at least establish themselves as a regular matchday squad member.

Strangely, Twickenham might be a good place for Byrne to make his case. Lose, even lose heavily, and the defeat is unlikely to be associated with the fly-half, given that Ireland have lost the last three meetings between the sides.

But win, and it's instantly the biggest moment of Farrell's tenure, and one with which Byrne's name is attached.

It is an occasion that will draw decidedly less fanfare than a Six Nations meeting. The stakes seem lower, but try telling that to Ross Byrne.

"Everyone's got a different temperament and Ross will be his own guy at the weekend and how Ross tends to play the game is very calm, cool and collected," said Farrell.

"I have no concerns whatsoever, he'll play his own game."