Towering high above Mumbai and far from the teeming shanty towns, a billion-dollar home, an oasis of ultimate luxury, is being built for the world's fifth-richest man. By Andrew Buncombe Anyone wishing to cast their eyes upon Mukesh Ambani's new house will very quickly find themselves with a stiff neck. The 27-storey tower soars huge and unmissable amid the greenery and quiet of the expensive Mumbai suburb of Malabar Hill. Abuzz with the noise of cranes and shouts of helmeted workmen, it is a human ants' nest of activity, set vertical amid the skyline of this booming city. Mr Ambani is reckoned to be the world's fifth-richest man and when his extraordinary property is completed in an estimated six months, the $1bn (£500m) building named Antilia will be the priciest house in the world. "Yes, it will be the most expensive," said a shopkeeper, whose humble store stands next to the tower. He handed over a newspaper cutting about Mr Ambani that he had pinned to the wall. Mukesh Ambani, aged 51 and said to be worth $43bn, is used to being in the headlines. Usually, it is about his business dealings as chairman and managing director of Reliance Industries, India's largest private company. Often it is about his infamous ongoing squabble with his younger brother, Anil, 49, a fellow industrialist with whom he fell out after their father's death; he is said to be the world's sixth-richest man. On other occasions it is for his free-flowing spending ...