Tests of Trefus

The tests of Trefus were two tests of physical strength which the fair-haired people of one planet were required to pass before being freed from slavery under the black-haired people. The first test required one of them to swim across a crocodile-infested lake, and the second demanded that they defeat their masters in. When the Second Doctor arrived on the planet, he helped the fair-haired people pass the tests of Trefus. In the first, he used explosives to temporarily stun the crocodiles, enabling Saul to complete the swim. In the second, he gave belts to the competitors (for "good luck") which became attracted to a magnet inside the TARDIS, enabling them to win. (COMIC: The Tests of Trefus)