NICE, France (AFP) - A British retiree on trial for murder and rape on the French Riviera was described in court on Wednesday as a sex-obsessed narcissist with a Jekyll and Hyde double personality.

Robert Dolby, 74, is on trial in the Mediterranean city of Nice for allegedly drugging and suffocating to death a British widow in 2010 and raping and attempting to kill another young woman in 2012.

It was the latter case which first landed Dolby in hot water.

In 2012, a partially-blind woman named Cindy, now 31, met what she believed to be a lonely, childless pensioner in a bar in Monaco.

She was looking for accommodation and he offered to let her share his home in the town of Beausoleil in France bordering the principality.

Cindy has told the court that his "paternal, protective" side quickly became overwhelming, and led to him declaring his love for her and a violent middle-of-the-night attack in which she was digitally penetrated and strangled near to death.

Investigating the attack, police stumbled on the suspicious death of another British woman, Annie-Claude Chevalier, a 60-year-old widower, while dining with Dolby two years previously.

Her death was declared natural as a result of a heart attack, but an emergency services worker raised concerns over Dolby's calm state of mind, lipstick stains on two cushions, and a blue tinge to her partially naked body.

Chevalier's body was exhumed after the attack on Cindy and traces of a powerful sleeping drug Zolpidem found in her system, the court heard.

An expert said the levels found indicated she had ingested it after arriving at Dolby's house.

A psychologist told the Nice court that Dolby had "in all likelihood a split personality, Dr Jekyll and Mr Hyde", on one hand he was a seducer and on the other overcome by powerful urges.

A psychiatrist separately testified that he displayed signs of "narcissistic perversion", capable of throwing out "seductive hooks" while at the same time being "emotionally anaesthetised, very cold".

Dolby, who lived on the French Riviera since 2005, was in 1991 sentenced to four years in prison in the UK for sexually assaulting a colleague who he invited to dinner.

He maintains he had consensual sex with Cindy, and that in the case of Chevalier, he had gone to the kitchen after sexual foreplay and returned to find her dead.