Leighton Hest is from the Oamaru stable of Phil Williamson, who has won the Cambridge race three times in the past four years - with Allegro Agitato (twice) and One Over Kenny.
Herlihy drove One Over Kenny (2007) and Allegro Agitato (2005).
Herlihy has also had wins in the Cambridge mile with Diamond Field (1994) and Buster Hanover (1997).
Leighton Hest won over a mile in 1.56.7 at the Harness Jewels meeting at Ashburton in May.
He is back to racing left handed tonight after a bold late run for fourth in the race won by Raydon at Alexandra Park last Friday night.
Sovereignty, who ran fifth in that race, is among the rivals for Leighton Hest.
Sovereignty, trained at Cambridge by Sean McCaffrey, won the Trotters' Mile last year in 1.59.9. He has won five of his seven starts at Cambridge.
Williamson is based at the Herlihy stable at Ardmore with Leighton Hest and Springbank Richard, who returned to New Zealand last Friday after a two-race campaign in Melbourne.
Springbank Richard is in the $100,000 National Trot at Alexandra Park next Thursday night.
Driver Ricky May has a fifth Ashburton Cup win in his sights on Saturday when he partners Second Wind.
The 4yr-old has won seven of his 10 starts, including the last three.
He won the Green Mile at Methven at his last start in 1.58, 0.2sec outside the race record.
May won the Ashburton Cup last year with Mr Molly.
He has also won the race with Cup Day (2006), Coringa It'll Be Mee (2002) and Balonne (1988).
Colin De Filippi will drive Slash An Burn for trainer Jim Curtin, who is at Westport.
De Filippi, who has also won the Ashburton Cup four times, has driven Slash An Burn seven times for three wins and three placings.
The combination was successful at Addington in October.
Curtin is driving the De Filippi-trained Minty Mellow in the Westport Cup.
Minty Mellow was a winner on grass at Motukarara last month.
Peter Davis will drive Another Homer in the Westport Cup for trainer Robbie Holmes, who is at Ashburton.
Another Homer has a sound form background.
Holmes has Biella Star in the Ashburton Cup.
