Oxford Children's Books Marv and the Race Day Cheaters

In book 10, Marvin and his classmates are at an inter-schools athletic championships. He's excited for the 100m relay team but thing become unexpectedly perilous when supervillian, The Champ, glides into the stadium on his scooter, flanked by cheetahs! A friendly sports competition has become the ultimate showdown between superheroes and supervillains! How can Marv win when his opponent can stop time itself?