A bid to buy a "magical" stretch of coastline for the nation has failed, the National Trust said.
The Trust had launched an urgent £2.6 million fundraising appeal to help it buy Bantham beach and the Avon estuary in south Devon, to maintain quality access to the sandy beach and protect the unspoilt coastal landscape for nature.
But the charity said it had been informed by the agents acting on behalf of the estate that it had been unsuccessful in its bid to buy the beach and the estuary.
The beach, nestling in the South Hams, has panoramic views over Bigbury Bay and Burgh Island which, with its Art Deco hotel and access by "sea tractor" at high tide, is the famous setting for Agatha Christie novels and TV adaptations.
If successful, it would have been the National Trust's most expensive coastal purchase.
The Trust was concerned that failure to secure the beach - described as the best surfing beach in south Devon - and the estuary for the nation could leave its future uncertain.
Mark Harold, South West regional director for the National Trust said the charity was "extremely disappointed" by the decision.
" We, along with many thousands of people who have contacted us over the past few weeks encouraging our involvement in its future, care very passionately about Bantham.
"We believe this is a very special place, held dear in the hearts of many, not only locally, but also those who have fond memories of childhoods and family times spent there.
"We will of course continue to care and protect for ever and for everyone the 40 miles and 3,000 hectares of the South Devon coast we already care for.
"We would also want, if possible, to work with any future owners of Bantham Beach & Estuary and ensure that this beautiful location is continued to be enjoyed by the many thousands of people who have told us how much it means to them."
He added: " We would like to thank everyone for their support of our fundraising appeal. As a charity the Trust relies on the generous support of its supporters who help us care for some of the most beautiful and vulnerable stretches of coastal land in the country."
Until now, Bantham's owners have protected the unspoilt nature of the estuary and surrounding countryside, which is in an Area of Outstanding Natural Beauty, and avoided inappropriate commercialisation of the beauty spot.
The entire estate, which has been in the same family for generations, was put on the market for £11.5 million but the National Trust decided not to bid for the cottages in the village of Bantham, saying its core purpose was not to be a social landlord.
The Trust had committed £4.6 million from its Neptune campaign fund for protecting coastal areas towards the proposed purchase.
It also launched a public appeal to raise another £2.6 million, to reach a total it hoped would allow it to buy the beach and estuary and pay initial management and conservation costs.