England's Danny Willett beat Spain's Jordi García Pinto 5 and 3 to capture the Spanish Amateur Championship at Pals near Girona.
A member of last year's Great Britain and Ireland Walker Cup side, the Rotherham player was one down after nine holes of the 36-hole final but birdied the 13th, 15th and 16th to go two up at lunch.
While he lost the 19th to a García birdie, the English Amateur champion won three of the next four holes to go four up.
Garcia cut the deficit at the 24th but Willett closed out the match with wins at the 29th and 33rd to join Darren Clarke, Jose Maria Olazabal and Sergio Garcia on the list of former winners of the prestigious King's Cup.
Ireland' s Paul Cutler suffered food poisoning and was forced retire after 13 holes of Saturday's quarter-final clash with Johann López Lázaro of France.
Spanish Amateur Open Championship (King's Cup) at Pals, Girona
Johann López Lázaro (Fra) bt Paul Cutler (Ire) retired
Daniel Willett (Eng) bt Benjamin Hebert (Fra) 2/1
Jordi García Pinto (Esp) bt Edward Richardson (Eng) 2/1
Eddie Pepperell (Eng) bt Guillaume Cambis (Fra) 2 up.
Willett bt López Lázaro 6/5; García Pinto bt Pepperell 3/2.
Final (36 holes)
Willett bt García Pinto 5/3.