When we did this tour in 2018, the RS tour did the tasting at Martel. It’s a smaller outfit. We were there 2 days early, so we took the tour offered by Tattinger. We planned to sign up for their tour at the Reims TI, but couldn’t make their computer work so the TI staff called for us. Tattinger rep said just to hurry down and join their English-speaking tour. It was excellent with a choice of champagne for tasting. Mumm’s was closed that day, although it was supposed to be open. All of the “houses” were an easy walk, although the RS tour guide taught us how to use the bus. We did a brisk walk from the TI to Tattinger in 15 minutes. Incidentally, we followed the Tattinger tour stopping by Martel, not knowing it would be our tour stop. We did a lovely personal tasting with the manager who spent considerable time explaining it all to us as we sat on a couch in the tasting room. I mention the date of our tour as things may have changed since we went. I believe Martel has since opened their cellars for tours.