Cordyline 15-16 was born a triplet and out of one of his better ewes. It was Mr Robertson's father, David, who saw his potential and picked him out just after weaning.
As a ram lamb, he took it to the Southdown progeny test site at Simon and Kirstin Engelbrecht's property at Stoneburn, where another 14 breeders were represented. That was when he first thought that "he measures up all right''.
Mr Robertson used him over a few 2-tooth ewes, following up from an artificial insemination programme, and his progeny were like lambs he had ``never seen before''.
They had very good bone, thickness and vigour.
The week before the ram fair, he took the ram to the Southern Canterbury A&P Show in Waimate - an opportunity to see how he measured up against other entries - and won champion Southdown.
When it came to the ram fair, Mr Robertson said he "thought he might go all right - but you never know''.
The ram was purchased by David Gillespie from the Midlands stud at Oxford and Mr Robertson retained semen rights.
Mr Robertson, who has about 70 ewes, was grateful for the support of other Southdown breeders.
They included Chris Medlicott, who lent him a ram when he first started the stud - and that ram featured in Cordyline 15-16's pedigree - and Ike Williams, who allowed him to send 10 ewes to a ram the following year and, again, that ram featured in the pedigree.
The Southdown breed society was a great group to be part of, Mr Robertson said.
He also thanked his family - wife Abby and their two young sons Hamish and Elliot. A ram sale on their property on Sunday sold out.
Mr Robertson wanted to improve the production of Southdowns and part of that involved their performance in the progeny test trial. He would like to see SIL recording figures tidied up between flocks.
There was excitement at being able to now measure intramuscular fat in sheep. A level above a certain threshold meant a big effect on eating quality, he said.
Sam and Deb Stevens, from the Cairnlea Poll Dorset stud, Poolburn, sold 82 rams at their on-farm sale on Friday for an average of $753, with a total clearance.
The top price was $2000, while the average price was up $70 on last year's sale.