Judges’ wildcard, Catriona Morison, has taken out the top prize beating finalists including Australia’s Kang Wang.

Scottish mezzo-soprano Catriona Morison is the surprise winner of this year’s BBC Cardiff Singer of the World, coming from behind to take out the top honours on Sunday.

Catriona Morison. Photograph: BBC

The 31-year old singer was the judges’ “wildcard” choice to compete in the finals against the four winners of the previous concert rounds. The other finalists were 29-year old Australian tenor Kang Wang, 32-year old American baritone Anthony Clark Evans, 29-year old Mongolian baritone Ariunbaatar Ganbaatar, and 30-year old English soprano Louise Alder.

The Guardian reported that there were “some gasps” from the audience when Dame Kiri Te Kanawa announced “the winner from Scotland”. Morison, who is currently a member of the ensemble at Wuppertal Opera in Germany, is the first British singer to win the prestigious competition, which was established in 1983 to identify singing stars of the future. Entrants must be under the age of 35.

Morison not only won the Cardiff Trophy and £15,000 (around $25,000) in prize money, but she also shared the Singer of the World Song Prize with Ganbaatar, which was announced on Friday.

The week-long competition featured 20 young classical singers, selected from 400 entrants. Sunday’s grand final took place at St David’s Hall in Cardiff, where the five finalists performed with the BBC National Orchestra of Wales.

Describing it as “an unexpectedly tight and high-quality final”, Slipped Disc said: “Two male singers – the Mongolian Ariunbaatar Ganbaatar and the Australian Kang Wang – seemed likelier winners, but the jury called it for the Scot.”

The judging panel for the final comprised Welsh National Opera Director David Poutney, mezzo-soprano Grace Bumbry, soprano Sumi Jo, baritone Wolfgang Holzmair and conductor Anu Tali.

Morison sang selections from Rossini’s Tancredi, Strauss’s Der Rosenkavalier, Ravel’s L’Heure Espagnole and Purcell’s Dido and Aeneas. The video clip below, posted on Youtube by anketwins, shows her performing the letter aria from Massenet’s Werther, Werther! Werther! Qui m’aurait dit la place, during Round Four of the competition.

The New York Times described her as having “a silky, lightly smoky tone, easygoing dramatic flair and unflappable poise”, while The Guardian called her “a singer of much character, real musical intelligence and the possessor of a mezzo voice that is wonderful in the expressive middle, though betraying a more patchy sound at the bottom and top of her range.”

Chinese-born, Australian-raised Wang is a lyric tenor and the son of two professional opera singers. He won praise from The Guardian who said that he “already sings like a top flight tenor, milking the top notes for all he’s worth, but doing it well. He sang two poets’ arias, Lensky’s and Rodolpho – poetic and emotional – but no Vincero, vincero, though he would surely have done it with Pavarotti panache.”

The BBC Cardiff Singer of the World takes place every two years. Previous winners include Finnish soprano Karita Mattila, Russian baritone Dmitri Hvorostovsky, Welsh bass-baritone Bryn Terfel and Swedish soprano Nina Stemme.