Murder mystery that has gripped India

Anil Ambani, one of the world's richest men, had been due to travel in the helicopter that he routinely uses to avoid Mumbai's notoriously gridlocked traffic. Then pebbles and gravel were discovered in the fueltank of his Bell 412 chopper. But, as officials from Mr Ambani's company claimed that a plot to murder the tycoon by his business rivals had been uncovered, the engineer who found the gravel during a routine inspection, was tense and anxious. Police who questioned Bharat Borge and his fellow engineers did not believe he was behind the sabotage but his family could tell he was concerned.

As police continued their investigation, Mr Borge's body was this week discovered alongside railtracks in the Vile Parle area of the city. Tucked inside his pocket was an apparent suicide note, addressed to the detective who had questioned him. "My parents have brought me up with the right values and I would never get involved in any wrong activity," he wrote. A post-mortem examination concluded that he died after mutiple fractures while at least one witness said they saw the engineer step into the path of an oncoming train.

The death of Mr Borge has added another layer of intrigue to a mystery that has gripped India. While police say they believe the 45-year-old took his own life or else was accidentally struck by a train - around 10 people are killed every day as a result of Mumbai's overcrowded commuter trains - his family claim there is something "fishy" about what happened and have demanded that the matter be taken up by the country's federal investigation body

In his note, Mr Borge - employed by an aviation contractor, Air Works - said he had been visited by officials from Mr Ambani's telecommunications and banking company, Reliance Anil Dhirubhai Ambani Group (ADAG) and that he was worried he was to be blamed for the sabotage. The company has confirmed its officials briefly met the engineer but said he had been praised for spotting the gravel and pebbles that could have brought down the helicopter. The police have also cleared the officials, saying they do not believe they said anything untoward to Mr Bharat, who was married with two children. Either way, having pondered the matter all night and spoken with his brother, Mr Bharat rose early the next morning and made his way to Vile Parle where his body was later discovered.

What has added to the mystery is that police believe that the engineer knew who was behind the alleged sabotage of Mr Ambani's helicopter - leaving him vulnerable to pressure both from the defectives pursing the case and from the culprits. Did this pressure lead Mr Borge to take his own life? "We are sure that Borge knew who had put gravel in the fuel box," a crime branch source told the Times of India.

Mr Ambani, 49, is one of India's wealthiest and most high-profile businessmen with a personal fortune estimated by Forbes magazine at around £8.1bn. He is famous for a long-running feud with his elder brother Mukesh, who is ranked as the country's richest man. Such has been the extent of the bad blood between the two men that Mukesh decided he and his wife could no longer live in the family mansion in Mumbai where the men's mother lives and has instead started building his own home.

In true Ambani style, that home, a 27-storey tower called Antilia in Mumbai's sought-after Malabar Hill neighbourhood, is expected to be the most expensive private house in the world with a price tag of around £670m by the time is completed. When Mukesh and his family move into the property, which will have six floors devoted simly for parking his cars, Anil will continue to live in the 14-storey home called Sea Winds that was built by their father, Dhirajlal, a former fuel station manager who developed the business that was split in half and divided upon his death.

So far, Anil Ambani, who can sometimes be seen jogging along Mumbai's Marine Parade in the earlly mornings, his chauffeur following behind with his car, has yet to publicly comment on the alleged sabotage plot. Nor has he said anything about Bharat Borge, the man who saved his life, only to take his own.