A farmer has won a $50 million payout from the state government over land set aside for a 100km super-highway through Melbourne’s outer suburbs.

The stunning court victory has “opened a can of worms”, an expert has warned, with hundreds of properties eventually needing to be acquired for the Outer Metropolitan Ring Road at an expected cost of $2.8 billion.

A planning overlay created a decade ago allows the government to claim land through the proposed road corridor, stretching from Werribee and Melton through Tullamarine towards Craigieburn, Epping and Thomastown.

But Wyndham Vale farmer John Kilpatrick only discovered the overlay in June 2017, when Wyndham Council refused him a permit to develop on his 60ha property.

According to court documents, Mr Kilpatrick sought compensation from Transport for Victoria but it “did not respond to the claim”.

The department tried to low-ball Mr Kilpatrick for less than what his land was worth before referring the “disputed claim” to the Supreme Court in October 2017.

An overview of the Outer Metro project. Source: Infrastructure AustraliaHe was paid “advance compensation” of $39 million in December 2018, but the Supreme Court last week awarded him a whopping $48,948,716.

Justice Gregory Garde determined Mr Kilpatrick’s land — which he had farmed on since 1972 — was worth $950,000 per hectare. The payout could skyrocket after costs and interest are finalised at a separate hearing.

Rail Futures Institute president John Hearsch said the “surprising decision” could leave the government open to more claims.

“There is always the potential other landowners within the reservation could launch similar compensation claims,” Mr Hearsch said.

“I wouldn't have expected the government would have budgeted for this.”

“Outer Metro is an important project vital to Victoria’s future transport needs but it's a fair while off yet.”

A Department of Transport spokesman said the government accepted the Supreme Court judgment.