Glasgow scrum-half Horne stole the headlines in the 61-0 win in Shizuoka which breathed new life into the Scots' Pool A campaign.
He is just the fifth Scotland player to score a World Cup treble, and follows in the footsteps of some of Scottish rugby's great names:
JOHN JEFFREY (v Romania, 1987 World Cup)
The Kelso flanker grabbed a hat-trick in the 55-28 win over Romania at Carisbrook during a pool match at the inaugural Rugby World Cup in New Zealand. Scotland scored nine tries in total to secure their place in the quarter-finals following an opening draw with France and a win over Zimbabwe. They would fall in the last eight to eventual winners, New Zealand.
IWAN TUKALO (v Zimbabwe, 1991 World Cup)
Selkirk winger Tukalo showed typical finishing prowess with three tries in a 51-12 win at Murrayfield. Co-hosts Scotland enjoyed their best ever World Cup, reaching the semi-finals where they lost narrowly to England.
GAVIN HASTINGS (v Ivory Coast, 1995 World Cup)
Watsonians full-back Hastings went one better and touched down four times against Ivory Coast in Scotland's first match of the '95 tournament in South Africa. A one-sided encounter in Rustenburg saw the Scots win 89-0. They would go on to reach the quarter-finals where New Zealand proved too strong once again.
ALLY HOGG (v Romania, 2007 World Cup)
A hat-trick from Edinburgh flanker Hogg was the highlight of 42-0 win over the Romanians at Murrayfield in front of 31,000 on a Tuesday afternoon. Rory Lamont chipped in with a try double in the pool stage win. The Scots would go on to lose out to Argentina in a nailbiting quarter-final in Paris.