At the age of seven, Colenso moved to Benson, a small village in rural Oxfordshire. Here, he appeared in his primary school’s musicals, sang in the choir and acted in youth productions with the local amateur drama society. He completed his secondary school education at the local comprehensive, Wallingford School. He attained an A* grade for GCSE Drama and was once again an active participant in the school productions. Colenso was also an avid rugby player, playing for a local club, his school and representing Oxfordshire on numerous occasions.