"The last 18 months have been horrendous," Andy Farrell says quietly as he contemplates his transformation from injury-ravaged union novice to the player around whom England hope to build a resurgence in next month's Six Nations. "It's been desperate and the hardest thing was that, with all these doubts about me coming from rugby league, I could never answer anyone. I'm the type of player that responds on the field and I couldn't do that because I was always injured. That brings real hurt."

Farrell's life since the RFU enticed him from Wigan to Saracens in March 2005 had been blighted by surgery on his foot, successive back injuries, including a prolapsed disc after a car accident, and a protracted dispute about his best position. Yet everything has changed in the space of six weeks. His selection for Brian Ashton's first squad as England coach has been accompanied by rave notices for his play at inside centre. His shrewd rugby brain, versatile skills and sheer presence could galvanise England.

And so Farrell's honesty when reflecting on his recent trauma is less a sign of frailty than confirmation that he has survived near-despair with his spirit intact. "The best way I can describe my progress is that I'm no longer having to think," he says as he prepares for his international debut in rugby union when England play Scotland on February 3.

"When I played league it came so easy to me. Good players don't have to think - and that's finally happening to me again at 12. I can go with my instincts and not have to think 'Should I be here or should I be there?'".

During the worst year of his life Farrell had little option but to agonise over his seemingly blighted fate. "When you're injured so long, it becomes very difficult - especially for a player like me who went seven seasons without missing a single match in league. It couldn't have come at a worse time, just as I set out on a new career in union."

He takes another sip from his second café latte of the afternoon in a corner of The Fox, a great old pub turned into a swish bar-cum-restaurant in Harpenden. With the contrast between Wigan and Harpenden even more obvious than the difference between a jug of bitter and a glass-stemmed latte, Farrell suggests it was "harder for [his wife] Colleen. Not only did we move south, with three children, but she had to pick me up repeatedly. There were many times when I'd say my career's over or that this move to union just wasn't meant to be. Colleen knew I wasn't really thinking that - but that's why I felt so sorry for her.

"In a rugby setting you don't want to show any weakness, so I would go to the club and try hard to put on this bright professional face. But when I got home I let out all my frustration and dejection. Richard Hill's girlfriend told me he was also terrible - but around the club he looked so strong."

Unlike the similarly injured Hill, who had given wonderful service to Saracens, Farrell had yet to even play a game for the club despite signing a lucrative three-year contract. "I wouldn't have felt great about being injured this long at Wigan but at least I'd given them 14 years as a player. At Saracens I just had massive guilt. All I'd do was slip in and out of [hospitality] boxes before and after games. I was like one of the staff."

He offered to pay back a large chunk of the money he had received from Saracens. "I spoke about it a few times to Nigel Wray [Saracens' owner] and he always said, don't worry about the club. He'd also text me to say he had no regrets about signing me - and even if they had to wait another year it would be worth it for the club. That's the calibre of the man."

It says much about Farrell's own character that he sidesteps his discomfort when remembering how, during the autumn, Saracens and England squabbled over whether he should be a forward or a back. He shrugs: "It was not something I could control - and while it was difficult, I was just glad to be training and playing. England wanted me to have a go at 12 and Alan Gaffney [Saracens' director of rugby] believed I had the makings of a 6."

He was depicted by some as an almost pathetic figure, a 31-year-old struggling to get to grips with the basics of back-row play. "Realistically, 12 is geared more towards league but I'd been interested in the forwards. But time was against us - especially with me wanting to force myself on to the international scene. In the end Andy Robinson [England's former coach] and Gaffney had a meeting. And then Alan said to me, 'It's up to you as it's your career.' That was very good of him - and I'm pleased to have played 6."

England, who have lost eight out of their last nine Tests, will simply appreciate the winning mentality he forged at Wigan. "There was a fantastically strict winning culture at Wigan," Farrell stresses. "When I first started [as a 16-year-old first-team player in 1991] there were players who didn't get on well together but that was because they were such strong characters. When it came to game-day we just believed we were going to win because everybody was so determined and training had been so intense. If you were not prepared to give 100% you'd be out the team - player power did that. We won all five trophies one season and our coach, Graeme West, still got sacked. But the players kept delivering because they put such pressure on each other."

Even at 16, sharing a dressing room with figures like Ellery Hanley, Shaun Edwards and Denis Betts, Farrell won respect for his mental toughness, extraordinary confidence and a zeal for training that meant he would outwork anyone in the most punishing routines. "There was so much hunger to prove yourself against someone like Shaun Edwards. He's now doing a great job as a coach [at Wasps] but he was very dominant at Wigan. Shaun was the ultimate winner."

Farrell's roots expose the soft underbelly of young union players today. "There are kids out there who are professional and train every day with the first team at their clubs. They think they've made it but they've basically done nothing. They might not have played a first-team game but they're earning an easy living.

"When I was growing up you trained with your own team and had to earn your right to make it into the top dressing room. I worked for three years as an apprentice joiner and even if I enjoyed the work I was determined to make it in league. But I wouldn't have dared go anywhere near the first-team dressing room until I was picked - there's much more complacency now."

A measure of his contrasting hunger and determination is evident in his otherwise touching memory of the only occasion he was ever dropped - at the age of 12. Haydn Walker, the coach of Orrell St James' Under-13s, left him out of the side for a cup semi-final. "He dropped me for disciplinary reasons, because I didn't like anything going against me at that age. It still scars me now."

He pushes his latte away and winces. "I shed tears over it and that's the last time I cried."

Farrell might have come close to breaking down numerous times over the past 18 months but he is finally in a position to add some old Wigan steel to a faltering England. In his last international league season he led Great Britain as they defeated Australia on their way to the 2004 Tri-Nations final and won the Golden Boot as the world's best player. Even in the painful interim he has not lowered his expectations.

"I've always been a talker in a team setting and I can't see that changing. I also think we can not only compete but challenge outright for the Six Nations and then have a very competitive World Cup. And if I'm part of that it will certainly get the nerves working again. It's been a few years since I had them so it'll be nice to feel them again."

Farrell leans forward in anticipation, his eyes suddenly gleaming. "There's no denying it," he grins. "I can't wait to get out on the big stage again."