What you call Polly on a Mopstick was known as Packhorses at Uplands Secondary Boys in Smethwick. Boy stood with his back to a wall, cradling next boy's head under his arm. The rest of the team form a back. The other team leapfrog on and the first win if they can call Packhorses, Packhorses, 1,2,3. before back collapses. Banned on school premises in my time. Late 60s early 70s. A rough game!