£2million basement for Rausing's horror house: Billionaire palatial extension at home where he hid dead wife Tetra Pak heir is returning to mansion in London's Belgravia after stint in rehab Plans for a two-storey basement include a swimming pool, gym and cinema Hans Rausing was convicted of preventing his wife Eva's lawful burial The 49-year-old his his wife's body for two months and told their servants she was still alive By David Wilkes Road to recovery: Hans Rausing appeared healthy and composed this week as he prepares to leave court-ordered rehab For two months, Hans Rausing hid his crack addict wife's body in their £70million mansion as he struggled to face up to her death. So as the Tetra Pak heir prepares to return home from rehab for his own drug abuse, it is perhaps only natural he is keen to make a few changes to the place. As one of Britain's richest men, of course, he has the resources to do it in style - and has plumped for a luxurious two-storey basement beneath the sprawling Grade II-listed property. The approved plans reveal that the underground development will include a swimming pool, gym, cigar room, wine store, plant room with rain water harvesting tank, cinema and lift. It will create 1,594 sq ft of extra floor space beneath the home, which is formed of two five-storey 19th-century townhouses and three linked mews buildings. The property, in London's Belgravia, already features a ballroom, courtyard, staff quarters and garages for up to seven cars. Rausing, 49, heir to the £4.3billion Tetra Pak fortune, is the latest member of the super-rich to join the trend for "iceberg" homes, where owners dig down below ground to create more space than traditional extensions. Based on other recent projects nearby in the wealthy borough of Kensington and Chelsea, it is estimated Rausing's basement - which is equivalent in size to nearly three average terraced houses - will cost £2million to build. And it is not only his house which is undergoing a transformation. Photographed this week leaving the Bluebird Café in Chelsea with a blonde woman said to be a "family friend" at his side, Rausing looked as though his treatment was doing him a power of good. His healthy appearance was in stark contrast to his gaunt look in early May 2012, days before the death of his 48-year-old American wife Eva. He was still sporting the beard he has grown since entering rehab, but the walking stick, Fidel Castro-style cap and unflattering hooped polo shirt he was seen wearing three months ago were all gone. Instead he was dressed smartly in a sports jacket and open-necked shirt, his wedding ring clearly visible on his finger. Mrs Rausing's remains were found in the couple's second floor bedroom at the house last summer after her husband was arrested on suspicion of possessing drugs. Improved: The 49-year-old heir was pictured looking gaunt and disorientated in May last year (left). One year on, (pictured right) he is planning to rejuvenate his Belgravia home where his wife Eva died Addiction: The society couple had allowed their 50-room Chelsea mansion to fall into disrepair and lived in a small part of the property before Mrs Rausing's death in May last year He had hidden her body for two months while maintaining a desperate pretence to servants that she was alive. Rausing was convicted of preventing her lawful burial and handed a ten-month suspended jail term. The judge at Isleworth Crown Court said Rausing was a tragic warning of the "utterly destructive" effects of drug abuse. He moved out of the house last year to undergo a rehabilitation programme at a private clinic. Denial: Mr Rausing hid his wife's body as he struggled to come to terms with her death. The 48-year-old was a regular at sociaety parties (left) but spent her last years as a recluse (pictured right in May last year)