The owners of a historic estate just north of Philadelphia have been forced to give it back to its previous owners.

The 42-acre Elkins Estate in Elkins Park had been owned by a financially troubled land conservancy now in bankruptcy.

The group has until Tuesday to appeal the forced transfer of the estate designed in a grand style rarely seen anymore. The home of a 19th century oil magnate, the estate has buildings by the same architect who designed the Philadelphia Art Museum.

For most of the 20th century, it was owned and maintained by the Dominican Sisters of St. Catherine de' Ricci.

In 2009, the order sold the property to the Land Conservancy of Elkins Park for $8.4 million. Since June 2010, the conservancy has not made a mortgage payment.

The last straw was the failure to make a Dec. 31 payment arranged by a bankruptcy judge.

The payment would have been possible, said conservancy executive director David Dobson, if it had not been for a deal with a bad lender.

"The lender committed in court to fund the deal and return escrow. That's why we signed a deal with a Dec. 31 deadline for the first $300,000 payment," he said. "We figured we had no problem ... we had $600,000 in escrow. We would just move it from here to here."

By the time the lender was forced to honor its agreement, the damage was done. The president of the Dominican Sisters, Sister Anne Lythgoe, said several attempts to hammer out a sustainable payment plan have failed. Their relationship with the conservancy had disintegrated, she said.

Now, the order is looking for a new buyer.

"Our pursuit is for a historic preservation with a really good economic model that sustains it, that doesn't convert it to condos or anything that is not appropriate to its historic nature," Lythgoe said. "Ultimately, there will be new owners, but we want to make sure the estate remains the beautiful treasure that it is. "

In the three years the Land Conservancy held the property, it made about $1.5 million in capital improvements.

Dobson says he intends to appeal the judge's decision to return the estate to the nuns.