★★☆☆☆As gimmicks go, it’s pretty impressive. A huge white dancefloor that fills almost the entirety of the Sadler’s Wells stage is tilted at a 34-degree angle. For the next 40 minutes, more than a dozen dancers will either surrender to gravity and slide down this makeshift wall, or struggle to defy the laws of nature by moving up and across the vertiginous incline.

This is Skid, the opening attraction in GoteborgsOperans Danskompani’s double bill. Choreographed by the Belgian-French artist Damien Jalet, the piece looks dramatic — how can it be otherwise? — but its choreography is inherently dull. At first you are entranced by the sight of this Swedish dance company in slow-motion freefall, the dancers slipping down the giant slope as if