King's University College will double in size after purchasing much of the adjacent St. Peter's Seminary lands in a massive deal.

Under the deal, King's University will acquire just over 18 acres of the land, located on Waterloo Street at Huron Street.

St. Peter's Seminary is owned by the Diocese of London. The land purchase includes a large swath of green space as well as the St. Thomas Aquinas Residence, which will be leased back to the diocese.

The diocese will continue to own the main seminary building and the dormitory where those studying to become priests live.

A bird's-eye view of St. Peter's Seminary, which is being purchased by King's University College. The land within the black outline is part of the purchase. (Supplied)

The deal is worth about $15 million; also on Monday, King's launched a $15 million campaign, called Imagine the Future. The student council kicked in $5 million while the alumni association will contribute $300,000.

"This land was intended for institutional educational use, and will remain so," said Sauro Camiletti, the interim principal at King's.

"We're preparing this land for the future of Catholic higher education in a way that hasn't been intended to in the past. We have students from 34 countries, we are a growing college, there's much we want to do to expand in the future. This land will also service the seminary, the diocese and our neighbours."

Green space to remain

The Old North neighbourhood where the seminary sits has raised concerns in the past about keeping the unique green space of the seminary grounds.

"Our neighbours will be enriched by what we do on this land and they will be engaged with what we do on this land," said Camiletti. "It'll be a community space. I'd like to see the land developed for academic purposes and I'd also like to see green space."

Camiletti said its unlikely student residences will be built on the site.

Bishop Ronald Fabbro said the land deal marks the end of an era.

"It will be for the future of King's and for our seminary. The collaboration that can happen between them is really enhanced today," Fabbro said. "It's the end of an era but I couldn't think of a better institution for it to go to."

Ward 6 Coun. Phil Squire said he'd like to see at least part of the land to remain a green space.

"The community is interested in the community access and the green space and King's has been open to that," he said. "There will be lots of talk going forward but at the end of the day, it's a piece of private property."