The Longbridge 100 Backyard Ultra is a continuous, multi-lap endurance event set in Litlington, Seaford, England. Operating on the unique Backyard Ultra format, this race challenges participants to complete a 4.167-mile (approximately 6.7 km) loop every hour, on the hour. The event proceeds until only one runner remains, having completed a final loop unchallenged. The Winter Edition introduces additional environmental factors such as colder temperatures and extended periods of darkness.