The environmental charity has agreed to buy Corehead Farm – “at market value” – which includes most of the famous deep hollow.

Farmers John and Berenice Williams will sell their 1,600 acres to the charity if the trust raises the money within 18 months.

The land also includes the western part of Hartfell which, at 808m, is one of the highest hills in the Southern Uplands.

BFT spokesperson Claire Doig said: “We’re delighted to be offered this opportunity by the Williamses. We look forward to working with them, their neighbours and residents in the Annan Water valley to secure the future of this wonderful and iconic area of the Southern Uplands for the enjoyment of future generations.”

The Devil’s Beef Tub is said to be where reivers hid stolen cattle and there is a martyred Covenanter’s grave at the bottom of it.

BFT plans to raise the money by applying to foundations and trusts, and through donations from the public.

Trust director Willie McGhee said: “We’re buying the farm at market value. The purchase of Corehead Farm is very important because it’s yet another piece of the jigsaw of the restoration of the ancient Ettrick Forest.”

The trust hopes to continue low-intensity livestock farming at Corehead, restore species-rich meadows and heather moorland, and expand the native woodlands.

Claire added: “The emphasis would be on community involvement with opportunities for educational activities as well as volunteering to realise this ambitious project.”

BFT has signed a legal option with the Williamses which allows them to purchase the land.

Mr and Mrs Williams said: “We are very happy that BFT has taken out an option to buy our farm as we know they will preserve the distinctive character of this very special piece of Scotland and are committed to environmentally sensitive farming”.

The couple will continue to live at Corehead Farm and no residential buildings are included in the sale.