'Where's mummy?': Traumatised boy, 4, cried for his mother after 'he saw her being stabbed to death at their £2million home in Britain's Beverly Hills' as banker husband is arrested on suspicion of murder 

A four-year-old boy was heard crying for his mother moments after he is thought to have watched her being stabbed to death at the £2million family home.

Police were called to the mansion in an exclusive enclave of Surrey dubbed 'Britain's Beverly Hills' on Saturday morning after a tip-off. 

They found 38-year-old Sonita Nijhawan lying dead in a pool of blood. She had been strangled and stabbed. A 46-year-old man, believed to be her investment banker husband, was later arrested.

Neighbours have said that Sonita was discovered by a relative who went round to the family home after receiving concerning text messages. 

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Tragic: Sanjay Nijhawan with his wife Sonita, above, who was found lying dead in a pool of bloody at their home

A man believed to be her husband Sanjay, was found slashing at his own throat and arms with a knife.

The couple's terrified son was seen being carried out of the property, as paramedics battled to save Mr Nijhawan's life. He was later taken to hospital with serious injuries, and then arrested on suspicion of murder.

He is currently in hospital receiving treatment for knife wounds to his throat and will be quizzed by detectives when he recovers. 

A neighbour who spoke to Mrs Nijhawan's father after he went into the house where the killing took place said: 'It was heartbreaking. I came back from an errand and saw Sonita's father on the drive. He was in tears and their little boy was with him.

'I saw the ambulance and went over to ask what had happened. I thought Sonita had fallen over or something but her father said she'd been killed. Their little boy was asking repeatedly, "where's mummy? Where's mummy?"

Stabbing victim: Accountant Sonita Nijhawan, 38

'I just put my arm around him and said, "mummy will be back soon." What else could I say?'

Another neighbour told the Sun Sonita had been discovered by her father.  

'I asked the father if there had been any indication of Sanjay doing something like this and he said he had never heard of him being violent to his daughter,' the neighbour said.

'He discovered what had happened because she had been in touch with him, so there must have been some sort of argument or dispute between Sonita and Sanjay.' 

Another neighbour said: 'Police believe it was a murder-suicide. Their four-year-old witnessed the attack and was left in the house until the police arrived.'

Detectives confirmed last night that Mrs Nijhawan had died from head and neck injuries, and said they were not looking for anyone else in relation to the incident.

The wealthy couple had moved into their newly completed home on a private estate only a fortnight ago. 

They had previously knocked down a smaller property on the site, which they had purchased for £925,000 in 2009.

The property is near St George's Hill in Weybridge, an area which has been home to wealthy residents including Cliff Richard, Ronnie Wood and former Chelsea striker Didier Drogba.

Last night friends said the couple had been excited about moving into their dream home and seemed to be in a loving relationship. 

Forensic detectives were seen going into the £2million mansion in Surrey earlier today to examine the scene

Sonita, 38, was found at a house in the upmarket St George's Hill area of Weybridge - dubbed Britain's Beverly Hills

A friend of Mrs Nijhawan said: 'I did not know of any problems between them.

'It was a love marriage. They got together 11 years ago after they met through a mutual friend.

'I saw her for lunch only two weeks ago with her little boy and she did not seem to have any problems. They seemed happy.

'He worked in the City and she worked for the family care home business. They didn't have any money worries. 

Investment banker: Sanjay Nijhawan=

'He is a family man who always seemed to be calm and peace-loving. I am totally shocked.' 

A neighbour who spoke to Sonita's father after he went into the house where the killing took place said: 'He told me police believe it was a murder-suicide.  

'Their four-year-old boy was in the house and witnessed the attack and was left in there until the police arrived.'

She added: 'Sanjay was quiet, sweet and soft-spoken. You couldn't imagine him hurting anyone.' 

And one of the couple's neighbours said: 'We met Sanjay a couple of times, he always seemed very nice and normal.

'When we first heard what happened we thought it was a burglary gone wrong, we never imagined anything like this.'

A friend who lives next to Sonita's parents in Twickenham, south-west London, said: 'Sonita was completely lovable.

'She was beautiful, kind and a loving mother. The family come from a strong Hindu background. Her father, mother and brother will be absolutely devastated.' 

Sonita was co-director of the family care home business, alongside her father and brother. The company owned three homes in Surrey and Twickenham, west London.

Her husband is understood to have earned an economics degree before working at Barlcays and ABN Amro. In 2009, he set up his own firm, Alphametric Solutions.  

Yesterday a relative at the family home said they were too upset to speak about their tragic loss.

A Surrey Police spokesman said: 'A 46-year-old man arrested on suspicion of murder remains in custody.' 

And Surrey Police Detective Chief Inspector Jason Taylor added: 'I believe this to be an isolated incident, with no wider threat to the local community.'

The estate known locally as 'The Hill' has exclusive grounds with a private members golf and tennis club

Exclusive enclave of gated estates that's home to some of Britain's biggest names

The shocking killing took place in an area that has for decades been a place of sanctuary for the rich and famous.

The tragedy happened in a house on a gated private road adjacent to exclusive St George's Hill, whose residents have included John Lennon, Ringo Starr, Kate Winslet, Sir Cliff Richard and Sir Elton John.

It has also attracted footballers John Terry and Peter Crouch and his model girlfriend Abbey Clancy.

The shocking killing took place in an area that has for decades been a place of sanctuary for the rich and famous, with residents including Peter Crouch and Abbey Clancy (left), and The Beatles star John Lennon

The estate, built in the 1920s and known locally as The Hill, has its own residents' association and within its 964-acre grounds are a private members' golf and tennis club.

It describes itself on its website as 'a distinctive and unique location designed for driven, motivated and successful high-achievers looking for a secure and private location in tranquil surroundings. The Hill is a place that provides an escape from the busy lives of its discerning residents.'

Houses on the complex and in the surrounding streets change hands for up to £13 million.

John Lennon's mansion on the estate, where he wrote the Sgt Pepper's album, is up for sale - for a staggering £14 million

Bollywood actress Shilpa Shetty and Dragons' Den star Theo Paphitis currently live at The Hill and recently hedge-fund managers, Russian oil barons and City financiers have moved in, attracted by the privacy and apparent safety.

However, some of the 420 homes there were hit by a mini-crimewave in 2011 which saw two violent robberies and a diplomat's wife and her son held at gunpoint in a £100,000 raid.