He tackles him with a couple of questions, polite but firm. Is this official merchandise? Does he have a licence to sell it?
The evasive skills are good. It depends what you mean by "official" or by "licence," guv; and the name Wigan Warriors is not a registered trade- mark.
Lunch will have to wait for a phone call to the club, telling them that, if it isn't registered, they must set about making it so right away. Life as a chief executive is a lot more complex than life as a player.
The last time Wigan played at Wembley, three years ago, Clarke was at loose forward for the last of his five winners' medals. Although he is still not 27, he will be sitting tomorrow with the old men behind the Royal Box, as an ex-player - one whose career was ended prematurely by a broken neck - and the brightest and busiest young administrator in the game.
It would be a difficult and painful transition for most people, but not, Clarke insists, for him. "I'm not a frustrated player any more. I don't want to run down the role of players, but I'm beyond that stage now. What I'm doing now represents my future."
When he does look back, he finds Cup finals do not really rank among the most vivid memories of his time with the club.
"I'm hoping to enjoy Wembley more this time. In all my time at Wigan, there are six games or so that really stand out and those were the ones we weren't supposed to win, like the World Club Championship in Brisbane. I got a special feeling playing for Great Britain when we beat Australia at Wembley, but in Cup finals we were always expected to win, so the main feeling was being anxious about losing," he said.
"I used to see players punching the air when we'd won and wonder what they were doing that for. They were games we always knew we should win."
If that sense of everything coming too easily was what drove Clarke to leave for the Sydney City Roosters, then he is finding all the challenges he needs in his new role at his old club.
The weeks since he took the job have been made up of long working days, raising standards that had slumped alarmingly right across the club. He never misses an Alliance or Academy game - "Because I might have to decide whether to keep them or release them," he said.
To those young players, he is the boss, although one with a distinguished playing record. To many of the first team squad, he is a contemporary and friend who must now keep his distance.
"I don't spend much time hanging around the changing rooms. That's not my place any more. And you don't have many friends in management; it's a lonely job."
Lonely and fraught with thorny problems. Had the timing and finance fallen differently, for instance, one of his first duties would have been to tell his closest mate from his playing days, Denis Betts, that the club could not afford to pay him.
There are other unpalatable tidings he has had to convey. Various functionaries have been told that, if Wigan win tomorrow, they must not join the team for the post-match pictures. When Clarke and his team-mates won in 1995, they were outnumbered on the photos by men in blazers; it rankled then, so he will not allow it now.
For an archetypal Mr Nice Guy, Clarke does not shy away from confrontation. Dodgy street vendors aside, he has ruffled feathers by telling the club's apprentices that they should have jobs and college courses on their timetables and not expect to be full-time professionals from their teens onward. "They were hanging around the club doing nothing. They aren't all going to make it, so telling them to have something else in their lives is being cruel to be kind," he said.
There have also been differences of opinion with some with a lot more clout at the club and arguments that make it just as well that he seems to have the unstinting support of Wigan's bankroller, Dave Whelan.
Clarke also caused alarm when he was quoted as saying that Wigan might one day be playing rugby union. "What I meant there was that a business has to look at all options," he said. "McDonald's were asked what they will do in the next century, if no one wants burgers and fries. They said that they will sell people what they do want. But sport isn't like selling fries. It's not just a business; there's so much tradition and feeling involved and our game's so good."
Therein lies something of a quandary. Clarke and the staff at Wigan are working hard to make the club the dominant force in the game again. But if they become too dominant it makes the sport a less viable proposition.
It is something else to ponder from the posh seats at Wembley. And, afterwards, he will be staying out of the pictures.Reuse content