LONDON - Prosecutors say British children's author Helen Bailey was plied with sedatives and likely suffocated by her fiance in a financially motivated killing.

The body of 51-year-old Bailey, a successful writer of novels for young readers, was found dumped in a cesspit in the grounds of the home she shared with partner Ian Stewart in July, three months after she was reported missing. Police also found the remains of her miniature dachshund near her.

Prosecutor Stuart Trimmer alleged that Stewart had fed Bailey a sleeping drug in a "long-planned, deliberate killing." Traces of the drug Zopiclone was found to have been in Bailey's body months before she died.

Stewart, 56, denies charges of murder, preventing a lawful burial, fraud and perverting the course of justice.