About 4000 Wiganers for mine. There was a big schools tournament on beforehand, so that helped boost the crowd a bit. Having said all that, the Lexus stand was the fullest of Harlequins fans I've seen, and that was my 4th visit. The kids were mostly behind the posts, and Wigan fans in the east stand.
Overall I'd say 4000 pies, 3000 Quins regulars, and 1000 newbies.
Didn't notice any serious marketing. I think the crowd came down to 4 things. The name of Wigan RL and the growth of their travelling support, the fact it was the first game of the season, the £10 ticket promotion and the schools tournament.
I go out of my way to look for RL news down here, and certainly didn't see more than a couple of small articles this week in the London press. I don't think there was any big scale marketing going on.