This deal is from the Green Point Pairs at Altrincham earlier this month. Despite there being thirteen top tricks only one pair bid the grand slam and only four pairs bid the small slam. The auction above is the succesful one by Alan Mould (North) and Raymond Semp (South). Alan and Raymond were playing support doubles, so three clubs followed by four clubs showed four card heart support. North now showed his spade control. South could now have bid four notrump RKCB, but decided to bid five notrump. North interpreted this as a grand slam force and with two of the top three heart honours bid the grand slam.
Other pairs may have had a more difficult time if East opened one club.
Thanks to Alan Mould for supplying the auction