Contracts are said to have been exchanged last week between the executors of Mr Clarke’s estate and the gas company for the original Poole’s Rock vineyard.

Mr Clarke, the former chairman of Macquarie Bank, founded the vineyard in 1988 in the Broke-Fordwich area.

He later acquired the Poole’s Rock estate and cellar door site at Pokolbin that was sold to the owners of the Audrey Wilkinson vineyard earlier this year.

Mr Clarke provided financial support to the Hunter Valley Protection Alliance’s campaign against AGL, and also lent his name to the efforts of the Hunter Wine Industry Association to have the vineyards excised from AGL’s vast exploration licence area. He died in April after a battle with cancer.

Protection alliance member Graeme Gibson said landowners were ‘‘locking the gate’’ to AGL and ‘‘David would be turning over in his grave’’.

Ian Ferrier, a trustee of Mr Clarke’s estate, has confirmed the sale.

Mr Ferrier said that ‘‘as a trustee you act to benefit the estate’’.

He declined to respond to further questions.

Last year, Mr Clarke said he believed AGL was not addressing the community’s concerns and it would mean the ‘‘death of tourism in the Hunter’’ if gas production went ahead.

Mr Clarke’s son Angus said yesterday the decision was out of the hands of the family and it was ‘‘obviously a sensitive issue’’.

He said the executors had made the decision to withdraw from the wine industry on the basis of the significant challenges facing it, and that AGL had approached them and been ‘‘decent to deal with’’.

An AGL spokeswoman said it was ‘‘currently in confidential discussions with a number of landowners in the Hunter project area to settle land access arrangements and land purchase arrangements’’.

The company would not comment on ‘‘speculation’’ but would advise of land purchases when transactions were completed, she said.