A lost portrait of Charles Dickens and 25 of his unpublished letters will go on display for the first time after a major acquisition from a private collector.

The Charles Dickens museum in London has bought a huge collection of objects belonging to the Victorian novelist, including a delicate chalk and pastel portrait by Samuel Laurence.

A lithograph of the portrait already exists, but the original was thought to be lost. It is likely to be from 1837, the museum said.

Among more than 300 items are 144 letters, offering a window into the author's life through his famously vivid prose.

One letter from 1857 describes getting lost on a walking tour with fellow-novelist Wilkie Collins, who sprained his ankle after the route "necessitated amazing gymnastics”.

In another, he answers fan mail, writing: "The mystery is not here, but far beyond the sky...”.

The collection, bought in the United States for 1.8 million pounds (2.3 million U.S. dollars), also includes a handwritten excerpt from "David Copperfield", original drawings by illustrator George Cruikshank, jewelry, books and a golden writing tool that doubles up as a pen and a pencil.

"This is a treasure trove – a true once-in-a-lifetime moment for the museum," said Cindy Sughrue, director of the Charles Dickens Museum.

"150 years after the death of Dickens, it is wonderful to be able to bring such a rich and important collection to the museum at his first family home."

The writer's great-great-grandson, Mark Dickens, said that "this quite staggering material brings us even closer to the man himself, his character, feelings, family and friends."

The objects will be cataloged and conserved at the museum - which is in a Bloomsbury townhouse Dickens' family moved into in 1837 - before going on display over the next two years.

(Cover photo: (File) Richard High from the collections team at the Treasures of Brotherton Gallery looks at a first edition of A Christmas Carol, by Charles Dickens. /VCG Photo