Wikipedia
High Cockalorum (also Highcockalorum or Buck Buck) is a mess game which involves two teams of roughly 12 people played in a large open space, such as a hall. One team, the supporting team, stands in a line at one end of the hall. The other team lines up at the opposite side. The other team must run as fast as they can and jump onto the backs of the supporting team. If all the players remain mounted for 10 seconds, the supporting team gets a point. They then swap over.
The game is also known as 'Polly on the Mopstick' in Birmingham, 'Strong Horses, Weak Donkeys' in Monmouthshire, 'Hunch, Cuddy, Hunch' in west Scotland, 'Mont-a-Kitty' in Middlesbrough, 'Husky Fusky Finger or Thumb' in Nottinghamshire, 'High Jimmy Knacker' in east London, and 'Wall-e-Acker' or 'Warny Echo' in north-west London. Those who grew up in Cardiff often called it 'Stagger Loney'; in Watford, 'Jump the Knacker 1-2-3', and 'Trust' in Lancashire. In South Africa and some Arab countries, it is (or was) known as ' Buck buck'.
Notorious for its danger, the game was banned in many schools in the 1950s after being popular in the Second World War.
A contemporary account from the unpublished memoirs of a Birmingham native born in 1919, Francis (Frank) Charles Woodley of Small Heath in Birmingham, reads as follows:
One game was played beside the brick wall of the local bread bakery, which was the rear wall of the ovens and was always nice and warm. We called this game Polly on the Mopstick, how it got its name is a mystery to me. We thought this was a great game and only played by the boys. If there were ten or so players, they were split into two teams by two appointed captains, picking players one at a time in turn. The idea was to pick big strong players were possible, with a couple of light members for agility. When the two teams were chosen, the captains tossed up to decide who was to be the 'horses'. The horse was made by standing a big boy with his back to the wall, he was the 'post'. The next boy then bent forward and put his head into the post's stomach, holding his arms around the post's waist. The next boy would then put his head against the second boy's rump and hold him around the waist. The rest of the team then did likewise until all were in position. The job of the opposing team was to vault onto the horse taking care not to touch the floor once on the backs of the horse. The captain would choose a light agile member to be the first jumper, who would take a running jump onto the backs of the horse, trying to get as far as possible in order to make room for the rest of the team. If all of the team did not get on the horse, then it was the turn of the horses team to jump on their backs. If all the team managed to get on the horse then the captain would shout in a loud voice "two, four, six, eight, ten, all my men are on and off again". If the horse collapsed because of the weight of numbers, then the jumpers were allowed another go. This very rarely happened because all sorts of tricks were resorted to by the horse to make some one touch the floor, and it would invariably end with a heap of bodies lying on the ground, laughing hysterically. We all thought it was great fun, especially in the Winter, for it was always nice and warm near that wall.