In Biggles Scores a Bull, Redbarns was the name of a farm near Warminster in Wiltshire. Its owner, one Captain Croft had a prize Hereford bull which was stolen by the cattle-rustling gang led by Walter Thellin in the fourth of a series of thefts of valuable bulls. Bertie, who had shadowed the gang from their base at Lockley Manor in Somerset, was attacked on the head and severely injured by one of the gang. His body was then left about two miles away.
Redbarns is a fictional location but Warminster is, of course, located in Southwest Wiltshire near the border with Somerset.