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.

He stuck to that line throughout the five-week trial, in which nine others were accused of playing a role in Mrs Pastor’s death. Four received sentences of up to 15 years and two were acquitted.

Remaining defiant under questioning, he dared prosecutors to "show me the proof". 

But in a dramatic U-turn, Janowski’s lawyer shocked the court on Tuesday by announcing that his client was “guilty of ordering Helene Pastor’s murder".

"These words which you wanted to hear from him come from my mouth. He tried to say these words, he wanted to say them but he couldn’t," Eric Dupond-Moretti told the court as Janowski sat crying in the dock.

Shortly before the verdict, Janowski expressed his “apologies” to his ex-wife and children in court.

His lawyer argued that this was a crime of passion to protect his partner Sylvia Ratkowski from her abusive mother but that he had not ordered the two hitmen to kill her driver as well.

That claim was forcefully contested by Janowski’s former personal coach Pascal Dauriac, who insisted the Pole ordered him to find the two killers and have them murder the driver and steal Mrs Pastor’s purse to make it look like a robbery.

A familiar face among the mega-rich of Monaco, Janowski was known for his charming manners and charity raffles, in which the prizes included fur coats and luxury perfume. He even ran a charity for autistic children which boasted Princess Charlene as a patron.

But prosecutors pointed to the fact that he had lied about being being a Cambridge economics graduate, and was an abject failure in business, with a string of failed ventures. He had haemorrhaged money despite dipping liberally into the €500,000 monthly allowance Mrs Pastor gave her daughter, which she described as “sweet money”.

Sylvia discovered to her horror after finally looking into the accounts, that her partner had overcharged her millions by getting her to sign “twice or three times” for the same luxury yacht and a house in London, and asking for a blank cheque every month.

“All these years when he lied to me and abused me by stealing my money,” she had told the investigating judge. “I had blind faith in him and he was the man of my life,” she said.

The sharp-suited businessman’s main motive was to get his hands on his partner’s inheritance after her mother’s death, said prosecutors.

Dauriac, the former coach, said Janowski first mentioned the hit in 2012 and again in 2013, when Sylvia, a cancer survivor, became ill.

"This cannot go on, Sylvia’s illness has deteriorated, we have to get rid of the old woman. Can you help me?" Dauriac quoted Janowski as asking him.

The coach told the judge he came under the “psychological sway” of Mr Janowski, who lavished him with gifts, trips to London and a business class flight to Thailand for two. He eventually caved in, asking his brother-in-law Abdelkader Belkhatir in nearby Marseille to help him find someone for a "big job”.

He said his brother-in-law found two men for the hit – Al Hair Hamadi, who acted as lookout, and gunman Samine Said Ahmed. Both were sentenced to life in prison.

A high point in the trial was when the jury were shown a view of Janowski’s initial testimony in which he confessed to the murder. In court, he claimed that version had been forced out of him under duress. In fact, the video showed the conversation was calm and cordial.

Mrs Pasto’s son Gildo, whom she had been visiting after he had suffered a serious stroke when she was gunned down outside the hospital, welcomed the verdict.

“This is an exemplary sentence. I always believed in Wojciech Janowski’s guilt,” said Mr Pallana-Pastor.

“The jury didn’t fall for his final manipulation, his last-last-minute confession, a final attempt to shirk his responsibilities.”