"Forget about slam when opps open bid firstly." some said. I think it's almostly a truth, at least for grand slam. But this is overruled with this board, when I was watching a star table:
South opened 1♦, the rest bidding was clear, simple and assertive:
dbl---2♦
3♠---4NT
5♥---5NT*precise King
6♥--7♠
dbl has shown at least 3 good hearts or 4. 7S was pretty sure.