Bonjour Ben. Thanks for your quick response to my question about RER service between CDG and Gare du Nord Sunday 21 May. The timetable you sent does show no services to Gare du Nord that day. Trains terminate after 5 stops for the whole day. I suppose there is a bus linking to Gare du Nord but I am trying to avoid multiple changes.
Merci for uoir help
Dang it. You're right. Sorry. I should have done more digging around. The RER-B blog lists that exact closure you're mentioning due to rail works between Le Blanc Mesnil and Gare du Nord.
I think in this case I'd suggest the CDG to Paris bus "Roissybus" as an alternative to the RER B train, so you don't have to switch from train to bus at some odd station. You can catch the Roissybus as early as just after 6am from either Roissypole bus loop or Terminal 2 bus stops. It'll terminate at Opera though, so a few stations away from Gare du Nord on Metro 7 or Bus 45.
Perhaps this will be a workable solution? Road traffic on Sunday morning should be pretty much non-existent so timewise I think Roissybus would be OK. Plus you'll see a bit more of Paris on your way in.