Complex sentence: After finishing at Wells Cathedral School Parry entered the Royal Marines, passed the Royal Marines Commando Training Centre, was selected by the Admiralty Interview Board and commissioned as a Second Lieutenant at the age of 18.
Split into simpler sentences: After finishing at Wells Cathedral School Parry entered the Royal Marines and successfully completed training at the Royal Marines Commando Training Centre. He was then selected by the Admiralty Interview Board and commissioned as a Second Lieutenant at the age of 18.