Poland’s former honorary consul in Monaco has been sentenced to life in prison for the murder of the principality’s wealthiest woman, Hélène Pastor, a day after he admitted ordering her death in a last-minute courtroom coup de theatre.

Mrs Pastor, a discreet 77-year-old at the helm of a €12bn (£10.5bn) real estate empire and dubbed Monaco’s “other princess”, was gunned down along with her longstanding butler and chauffeur, Mohamed Darwich, 64, in Nice on May 6, 2014.

The Monaco court handed sentences to Wojciech Janowski, 68, former partner of Mrs Pastor’s daughter Sylvie, along with the gunman and an accomplice who acted as lookout.

His former personal trainer was sentenced to 30 years. During initial police questioning, Janowski had confessed he “ordered this murder” and to paying his fitness coach €140,000 to organise the hit.

He had alleged that Hélène Pastor and her son Gildo had made her daughter’s life a misery and that it was his moral duty to put an end to it. “How many times did I find Sylvia in pieces? (The murder) was to put a stop to the suffering of my wife,” he told investigators.

But he later changed his tune, saying his “poor French” meant he had misunderstood the questions and pleaded innocent. In fact, he said, Mr Dauriac had ordered the murder to pressure him into paying “protection money” or see his children kidnapped.