The circumstances behind the death of a one-month-old baby girl in Chesham will never be known, a coroner has ruled.

The cause of Darcy Smith's death was unascertainable at a post mortem examination, an inquest at Beaconsfield Coroner's Court heard.

Darcy had been sleeping on an L-shaped sofa, with her mother Donna sleeping on the other arm of the chair, on May 14 last year at their home in Deansway. Mrs Smith woke that morning to find Darcy had died.

Dr Alexander Kolar, who carried out the autopsy, said it was possible Darcy could have been a victim of an "unsafe sleeping environment" caused by co-sharing the same bed.

Possible risks include the baby overheating and the amount of available oxygen decreasing, he said.

But Darcy's mother told the inquest: "I wasn't anywhere near her."

Her grandmother, Catherine Collier, said: "It seemed everyone was implying Donna was sleeping with Darcy - she wasn't."

Police were called in as part of the investigation into Darcy's death, but the inquest heard this has now been closed.

Coroner Richard Hulett said: "I think this is probably as far as we will ever get. It's against the background of circumstances that are known to be risky.

"What I have [in terms of evidence] is very sparse indeed. The cause of death has to remain as unascertained.

"In these circumstances I have to give a short narrative verdict, that Darcy was found to be deceased on the sofa.

"There's not a cause of death - we are never going to be any the wiser."