Fileman threw 49.06m to take gold at the Morton Stadium on his second international appearance.
Last month the Ivybridge Community College pupil had won a bronze medal on his international debut at the SIAB International in Wales.
The Youth Nations Cup was an under-18 match between England and Ireland. Fileman and fellow England under-17 thrower Kane Aubrey took a one-two in the discus against their older Irish rivals.
Wimborne’s Aubrey threw 48.48m for second, with Ireland’s Adam Sheridan taking bronze in 48.35m.
Meanwhile, City of Plymouth’s Emily Bee got her first taste of a senior heptathlon competition when she guested at the Combined Events International in Manchester at the weekend.
Bee won the under-20 prize and finished ninth overall in a field that included three Commonwealth Games athletes and the Polish Under-23 champion.
The Plymouth High School for Girls pupil, who is only in her first year at under-20 level, only had a fortnight’s preparation for the competition, but still performed well, scoring 4,868 points.
She did set a new PB in the 100m hurdles with a 14.30 second run. Bee also leaped 1.65m in the high jump, threw 9.03m in the shot, ran 25.75 seconds for the 200m, recorded 5.43m in the long jump, threw 33.89m in the javelin before clocking 2:35.83 in the 800m, despite suffering in the last 300m.
The international event featured a senior match between England, Wales, Scotland and Northern Ireland, with Bee one of six guest athletes invited to take part.
Competing in a senior heptathlon will have been good experience for Bee, who is the South West Schools’ champion.