Whortle's Hope by Robin Jarvis
It is almost the time of the Fennywolde games, when the young field mice compete to see who will have the honour of being the head sentry of the cornfield for the entire summer. Young Whortle longs to win the competition but not if it means his friends are going to sabotage the other competitor's chances. He wants to win on his own merits but soon realises winning isn't the most important thing as another mouse needs the prize more than he does.