He was born in Bebington, Cheshire to Roger Lancelyn Green and June Green. His father was an author known for his popular adaptations of the Arthurian, Robin Hood and Homeric myths, and his mother was a drama teacher and adjudicator. He attended Bradfield College in Berkshire, and then University College, Oxford, where he earned a degree in English.After leaving college, he travelled extensively, throughout Europe, India and South-East Asia.

He was a collector of Sherlock Holmes-related material, and was co-editor of the first comprehensive bibliography of Arthur Conan Doyle, A Bibliography of A. Conan Doyle, with John Michael Gibson, and also a series of collections of Doyle's writings that had never before been collected in book form: Uncollected Stories (1982), Essays on Photography (1982), and Letters to the Press (1986), all co-edited with Gibson. The Conan Doyle bibliography earned Green and Gibson a Special Edgar Award from the Mystery Writers of America during 1984.

Lancelyn Green also published other books on his own. The Uncollected Sherlock Holmes (1983) anthologized Doyle's non-canon Sherlock Holmes writings, The Further Adventures of Sherlock Holmes (1985) is a collection of Holmes pastiches and parodies, and Letters to Sherlock Holmes (1985) collected the most interesting of letters to Sherlock Holmes, arriving at the headquarters of the Abbey National Building Society, whose address in Baker Street was the closest to the fictional "221b".

He was something of a showman, appearing as a 19th-century music hall master of ceremonies at events of the Sherlock Holmes Society, of which he was chairman from 1996 to 1999, and dressing in period costume to visit Reichenbach Falls, where Sherlock Holmes was thought to have died until Conan Doyle "resurrected" him eight years later. For his encyclopedic knowledge of Arthur Conan Doyle and Sherlock Holmes, and for his masterful scholarly works, he was well regarded among scholars of Holmes.

Later in life, he worked extensively on notes and collecting material for a planned three-volume biography of Conan Doyle, which remained unfinished at the time of his death. He lamented the legal wranglings needed to gain rights to Conan Doyle's private papers and manuscripts, which were planned to be sold at an auction.

As early as the age of seven years Richard began his collection of Sherlockiana, and created his version of 221b Baker St in an attic room at Poulton Hall, gleaning material for a few shillings at junk shops and from the family's own Victoriana. Later he began to assemble his literary collection, and would add any edition of Doyle's output, as well as posters, ephemera and novelty items with a Sherlock Holmes theme or Doyle association.

By the date of his untimely death he had been collecting voraciously for more than 40 years and without doubt possessed the largest collection of Doyleiana that existed privately (and probably the largest such collection that ever could exist now that it has been bequeathed to the City of Portsmouth)

Packing the collection took two weeks for a team of ten and in total filled 12 vans. It comprises approximately fourteen thousand volumes and some two hundred thousand other items. The collection is currently in the fourth year of being catalogued by the City of Portsmouth Museum where exhibitions have created much interest. The patron of the collection is Stephen Fry.

Lancelyn Green suspected that the Conan Doyle papers being auctioned at Christie's were part of a collection that Dame Jean Conan Doyle, the author's daughter, actually wanted the British Library to have. He attempted to stop the auction, but was unsuccessful.

In the weeks before his death, he told friends and journalists that an unidentified American was following him, and that he feared his opposition to the auction could endanger his life. His behaviour became increasingly erratic, and once he insisted on speaking to a visitor in the garden because he said his apartment was bugged.

During the night of his death, his sister telephoned his apartment, obtaining only his answering machine, which had a new message with an American voice (this was found later to be the standard message tape supplied with the machine). Her worries about this resulted in the discovery of Lancelyn Green's body, face down on his bed, garrotted with a shoelace that had been tightened with the handle of a wooden spoon.

Murder was suspected, and there was some newspaper gossip. Because the CID was not called at the start, any evidence that might have been useful for a murder enquiry had been disturbed or removed during the course of dealing with the body.The Coroner returned an open verdict. Many of Richard's best friends thought it was not in his nature to commit suicide. However, some thought the death to have been an elaborate suicide, intended to seem like murder, in order to cast suspicion upon one of his rivals. This replicates the plot of one of the last Sherlock Holmes mysteries, The Problem of Thor Bridge, in which a woman commits suicide in a manner meant to implicate the woman with whom her husband had been flirting.

During August 2004, it was announced that Lancelyn Green had bequeathed his extensive collection of Arthur Conan Doyle to the Portsmouth Library Service. Lancelyn Green had chosen the city because Conan Doyle had a medical practice there, and it was where the two first Sherlock Holmes books were written.