Williams' input as forwards coach for Munster's 2006 and 2008 Heineken Cup-winning campaigns helped net his new post as assistant coach to new Australian boss Robbie Deans.
There are some great experiences to cherish. I remember turning up for my first training session. I had just won the Super 12, as it was then, with the Brumbies for the first time in 2001, having lost the final by a point in 2000, and I was feeling pretty good about myself and my rugby.
So I turned up for that session and we were doing some line-out work. David Wallace and I had been pushed out of the line-out, which was good because I could properly watch what followed. Peter Clohessy was lining up against his brother, Des; a young Alan Quinlan was in there. And something went wrong, and Quinny punched someone. Then Des waded into his brother and suddenly it was a free-for-all punch-up. Mick Galwey, the coach, was in there belting his own players.
So my first impression was that these guys were mad. I remember ringing my agent and saying: 'What the hell have you got me into here? These blokes are beating the crap out of each other as much as they do the opposition.'
But the one thing it showed me was their intensity. It is one of the main reasons they do so well. People in the past questioned the skill of the players and that Munster maybe did not look so good on paper, but when we got on the field that intensity and our work-rate made up for a lot of that.
SIX days after departing Cork and leaving Munster to their Heineken Cup celebrations, Jim Williams reported for work with the Wallabies.
Making the transition from the end of the northern hemisphere season to the other end of the world, where the international calendar is just beginning, cannot be easy. The Wallabies kick off their season on Saturday, and there will be a touch of spice to Williams' first game as Australian assistant coach: he must plot the downfall of Ireland and a Munster pack he sculpted into a collective powerhouse in his former job.
Insider knowledge will be spoken about in the press this week and already Wallabies head coach, Robbie Deans has said of his new recruit: "Jim will draw on his knowledge, just as they will draw on their knowledge of Jim."
It's Monday morning at St Xavier College in the Melbourne suburb of Kew. This is a city where Aussie Rules rules, and rugby union finds itself down the pecking order in terms of popularity.
The Wallabies, however, are doing their part to reach out to a wider audience. Williams, now dressed in green and gold Wallaby gear, oversees a drill in which nine schoolboys from the Melbourne area were invited to train with the Wallabies for a morning. It was Deans's idea, someone from whom Williams says he has learned an awful lot in a short space of time.
"Robbie is excellent," acknowledges Williams. "He knows where he wants to go and how he wants to do it. Certainly it has been an eye-opener so far working with him."
The new Wallaby coach, who many in New Zealand feel should have been taken over from Graham Henry in the All Blacks hotseat following last year's Rugby World Cup debacle, has already made a huge impression on Williams.
"What impresses me most is his attitude -- he's very calm, relaxed and just dictates at the right time. It's all about the players with him. It's good from that perspective to see that. I've been sitting back a little bit watching that, and I've learned a lot in a week."
As a player Williams very quickly bought into the Munster style of forward play and, later as forwards coach, educated the next generation who went on to win two Heineken Cups in three years.
However, there must be an element of culture shock as he enters a scenario where the Australians would not be recognised for their strengths up front. "Obviously with the rules over here, it has been a little bit different, particularly the way they do scrummaging and the way they do line-outs. But I'm coming back trying to give my perspective and the guys have received it very well."
He admits leaving Munster tugged at the heart strings, as was obvious in those emotional moments following the final whistle in Cardiff last month.
While photographs captured a tearful Williams celebrating a second Heineken Cup triumph, his strongest feeling at the final whistle was one of relief. He admits there was pressure on himself and the pack to perform while he makes no apologies for the manner in which Munster closed out the game against Toulouse.
"I didn't think we had been consistent in the games leading in -- we just weren't showing any kind of form. I know we were chopping and changing sides but certainly we needed to make sure the set piece was right, get that maul back working. We did a lot of work. There was a lot of pressure coming in for myself personally and for the forwards to make sure that we could play well against Toulouse and match them in the set piece, and we did that superbly.
"I know people are complaining about this kind of style - picking and driving - but we worked to a game-plan and we stuck to it. We didn't take the ball wide but we made ground with Doug (Howlett) coming in. We certainly worked the game-plan to perfection."
It won't be first time he will hear a question about the importance of his knowledge of Irish rugby, but he smartly plays down its significance.
"It will only go so far - with the quality of players Ireland have, they're smart enough to know exactly what I'm thinking and what they're thinking. It's one of those things like getting the basics right: making sure you can win your set piece, get over the advantage line and create space.
"They know as much as what I know. Realistically that's not going to count for too much."
He watched Ireland on Saturday against the All Blacks, admired their intensity at the breakdown which he said "is what I would expect from those kind of boys", and said the awful conditions would have impacted on the lineout.
He acknowledges that Saturday's test for Ireland will be a huge game both mentally and physically after they began their 53rd week of the season.
"It's asking a lot of those guys, coming off such an intense season. I suppose we were a little bit selfish with the Munster team, with the forward pack coming through that season. They came back from the World Cup then went into a Six Nations - that's asking a lot of players, especially when you're talking about 10, 12, 13 forwards that haven't been rotating a lot."