Redwood

The first four bids should be commonplace, but how the auction develops from there is far from clear.  North is still aiming for game in no trumps and will either bid it directly, or might bid his diamond control as shown with some concern over the quality of his hearts.  South has too much shape to leave either of these bids.  I would take 4♣ to be forcing on this hand which has already forced to game with a new suit at the three-level, but is not a slam-try in itself with no suit agreed even by implication.  Once again North has a difficult choice.  My preference is to agree clubs, but there is certainly an argument for spades, particularly in pairs.  I have shown a redwood bid agreeing clubs by implication, but your partnership agreements need to be very sound before you try this route.  When South shows two aces and the trump queen North can hardly do less than bid the slam.

15 to 18 1NT rebid, checkback

I favour this high range for the 1NT rebid making room for a forcing 2NT rebid on nineteen or twenty points.

2♣ from South is checkback promising at least invitational values, and 2NT from North shows the upper range and is game-forcing.

From this point the bidding progresses as above.

What happens?

Spades always makes twelve tricks on the 3-2 split losing just one trump trick.

Clubs actually makes thirteen tricks if you dare risk ruffing the third spade high but I would not wish to be in the grand requiring, as it does, a 3-2 split in both black suits.

As the spades have to be brought in for either contract 6♠ is probably the best contract in pairs but I would feel a little safer in 6♣ at teams for the loss of just one imp.

Intermediate and above