The religious order that owns the grounds at Clonkeen College school in south Dublin was in discussions to sell its playing fields as long ago as May last year - but did not tell the school.
An approach by developer Patrick Durkan Snr came just weeks before the school presented its own plan to the Edmund Rice Schools Trust for the development of an all-weather facility on the same playing fields.
The charity is legally responsible for the congregation's schools and its property.
While Clonkeen College awaited a decision on its proposals, the Christian Brothers continued negotiations with Mr Durkan and his associates.
It is understood the sale was agreed between the parties last September - a full eight months before the congregation's representatives informed the school of its intention to dispose of the lands.
Records held at the Companies Registration Office show that two special purpose vehicles relating to the lands' acquisition - Clonkeen Asset Management and Clonkeen Investments Designated Activity Company - were established in July and October of last year respectively.
Peter Horgan of Lugus Capital is listed as a director with both companies.
Binding contracts for the sale of the school playing fields are understood to have been signed two months ago - a month before the Christian Brothers informed the school's board of management of the deal.
A spokesman for Mr Durkan declined to comment when contacted by the Herald yesterday.
Clonkeen's principal Edward Melly has been strongly critical of the Christian Brothers' conduct.
Mr Durkan and a consortium of private investors assembled by two former brokers at Davy have emerged as the buyers of 7.5 acres of playing fields at the school.
The Christian Brothers are set to secure in the region of €18m from the sale.
The brothers have said the school will receive 3.5 acres and €1.3m from the deal.
Mr Durkan first approached the order in May of last year to express his interest in acquiring the land.
The approach is understood to have been readily received by the Christian Brothers and the Edmund Rice Schools Trust.