Children's author Helen Bailey was secretly drugged by her partner before being killed in a "cynically executed murder that had money as its driving motive", a court has heard.
The 51-year-old's body was found in a cesspit in the grounds of her home in Royston, Hertfordshire, in July, having been missing since 11 April.
Her partner Ian Stewart, who she was due to marry, suffocated her and dumped her in the pit, a jury was told.
Mr Stewart, 56, denies murder.
The author, who created the Electra Brown series for teenagers, was worth "approaching £4m", St Albans Crown Court heard.
The couple had met online following the death of Ms Bailey's husband, John Sinfield, in 2011, and moved in together a year later, buying the house in Royston together for around £1.5m.
Prosecutors told the jury they had made arrangements for Mr Stewart to obtain the house and "substantial financial advantage" in the event of Ms Bailey's death before the wedding - which was due to take place "imminently".
Stuart Trimmer QC, said, it was "a long-planned, deliberate killing, a cynically executed murder that had money as its driving motive."
The court heard in the hours after killing her, Mr Stewart had amended a monthly standing order from Ms Bailey's account into his from £600 to £4,000.
During the time Ms Bailey was supposedly "missing," it is alleged Mr Stewart had twice requested copies of her will.
On her death, he would benefit to the sum of "£1.8m in addition to the sum of the main Royston house and the second home in Broadstairs", Mr Trimmer said.
He told the jury Mr Stewart had been giving Northumberland-born Ms Bailey sleeping pills for several months, before killing her on 11 April 2016.
Records show the author had been Googling: "Why do I keep falling asleep?".
Mr Stewart "killed her, probably by suffocation whilst she was sedated by the drugs he administered", Mr Trimmer said.
A drug used to treat insomnia, zopiclone, was found in her system, which had been prescribed to Mr Stewart, the court was told.
Ms Bailey was reportedly last seen walking her dog Boris, a miniature Dachshund, near her home on 11 April.
The same Day, Mr Stewart was seen dumping a "large white object", alleged to be a duvet at a refuse tip, it was said.
Mr Stewart reported her missing four days later.
He then joined in searches and appeals to find his partner, despite knowing her body was in the cesspit, the prosecution alleged.
He also sent several emails to her during April in which he "professed his undying love for her."
Mr Trimmer said: "The whole course of conduct [was] designed to deceive the police and the local community… into believing that she had just left home."
Ms Bailey's body was found three months later alongside that of the dog, in the pit beneath the garage.
Mr Stewart failed to tell police about the cesspit's location and had attempted to hide it by parking Ms Bailey's Jeep over it, the court heard.
When officers found it, they saw a human arm protruding from the effluent material. The remains of the dog were then discovered.
The court was told the dog had to be killed to support Mr Stewart's claim Ms Bailey had left their home, as she was "devoted to Boris, and the notion that she would have left home without him was unthinkable".
Jurors are expected to visit the couple's home later this week.
As well as murder, Mr Stewart is also charged with fraud, preventing lawful burial and three counts of perverting the course of justice.
He has denied all six charges.
The trial, expected to last seven weeks, continues.