Adrian Cohen is the creator of Costello, a project he started in 1995 in order to give his students motivation in studying English reading and writing. After graduating from Cambridge University he started a career in English teaching in Japan and took his masters in TESOL/TEFL at Birmingham. He was made Associate Professor at Iwate Prefectural University in 2003 before returning to the U.K. in 2005 to work full time on developing Costello as a teaching and learning tool. He currently lives in Manchester with his wife and three children.

James Hobbs was born in Leeds, England. He has been teaching English in Japan since graduating from the University of Kent at Canterbury in 1991, and also holds an MSc in TESOL from Aston University. He has extensive experience of teaching in high schools and universities in Japan, and since 2002 he has been a full-time lecturer in the Department of English at Iwate Medical University, teaching both general English and medical English classes. He lives with his wife and two young children in the northern Japanese city of Morioka.