Croon's property had sat on the market for $3.5 million for a number of months in 2013 but did not sell.
James Conquer then approached Croon and advised him he knew of a potential buyer, who turned out to be his fiancee.
There is a dispute between the parties about when Croon knew that Maxwell was engaged to Conquer but it is agreed he was aware of it before the property changed hands in the second half of last year.
There were negotiations over the price of the property between Croon and Conquer in July last year and it settled in September, selling for about $3.1 million.
The Conquers last December sent a proposal to Croon for him to lease the land where his bloodstock business was operating for $80,000 a year for five years. But Croon rejected this and told the Conquers he believed the five-year lease was already included in the purchase price, which they say is the first they had heard of this idea.
He was given an order to vacate the property.
Croon then went to the High Court, claiming the parties agreed that the price of the property was reduced from $3.5 million to $3.1 million to reflect him prepaying the lease for five years.
Croon has brought a claim against the Conquers alleging Maureen Conquer and the trustees who now own the property made misrepresentations to induce him to enter into a contract.
Second, Croon says he had a mistaken understanding when entering into the deal and alleged Conquer and the trustees knew this was the case but did not put him right.
He is either seeking a cancellation of the sale agreement or $400,000 compensation.
Croon also alleges James Conquer breached his duties to him by preferring his own interests and those of his now-wife over his client's interests.
Croon this month sought an interim injunction, effectively letting him keep his business on the land while this wider dispute is resolved.
This was denied by Justice Susan Thomas, who said the mistake plank of Croon's claim was unlikely to succeed.
"The evidence shows that, at best, any mistake was in Mr Croon's mind as his own affidavit appears to acknowledge," she said.
In dismissing the application, Justice Thomas said Croon's business had six weeks to find alternative accommodation for the horses and vacate the property.