From a Loughborough University website:
“Maths Battle” is a simplified version of the Russian “Матбой”. The pupils are given ten problems to solve on their own for about an hour (see a sample list). Then they are split into two teams and given some time in different rooms to discuss their solutions and the strategy of the battle. They also choose a captain. The battle begins with the “Duel” in which the two captains are presented with a small puzzle to solve. The winning captain starts the battle which consists of challenging the opposite team to solve a particular problem. The details of the rules can be found here.
For more information about the Maths Battles contact Professor Alexander Veselov in the Maths Department.