One So Wonderful was a bay filly with a small white star bred by Egon Weinfeld's Meon Valley Stud in Hampshire.
[5] Like the other horses raced by the Meon Valley Stud, One So Wonderful competed in the black and white colours of Helena Springfield Ltd a company owned by Egon Weinfeld.
Ridden by the veteran Pat Eddery she took the lead a furlong from the finish and accelerated clear of her thirteen opponents to win easily by eight lengths.
[9] For her only other race of the year the filly was moved up in class and distance for the Sun Chariot Stakes over ten furlongs at Newmarket racecourse on 4 October, when she started second favourite behind the Oaks winner Reams of Verse.
Ridden by John Reid she led for most of the way and got the better of what was described as a "thrilling battle"[10] with Kool Kat Katie in the final furlong to win by a neck, with Reams of Verse three and a half lengths away in third.
After a two-month break from racing, the filly was returned to all-female competition for the Listed Golden Daffodil Stakes over ten furlong at Chepstow Racecourse.
[13] In August One So Wonderful was stepped up to Group One class for the first time when she was one of three fillies in a field of eight runners for the International Stakes over ten and a half furlong at York Racecourse.
Ridden by Eddery, she was the 6/1 fourth choice in the betting behind Faithful Son (winner of the Prince of Wales's Stakes), Chester House and Limpid (Grand Prix de Paris).
She was among the leaders in the start and despite coming under pressure in the straight but made steady progress along the inside rail and took the lead on the line to win in a three-way photo-finish from Faithful Sun and Chester House.
[2] The best of her foals was Sun Boat, a gelding sired by Machiavellian who won the Grade II San Diego Handicap at Del Mar Racetrack in 2007.