By Jonny Turner They’ve made their mark again on the national yearling sales, and now Stonewall Stud will be out to conquer Cromwell. Trainers Steve and Amanda Telfer bring three horses south just a couple of days after their team set a new Australasian record for purchasing a trotting yearling. A filly by star North American stallion Walner from Egee Money was purchased by the powerful stable for $290,000. The blueblood squaregaiter is among 12 yearlings Stonewall Stud bought out of the Christchurch sales ring on Wednesday, following their purchase…