A woman is being held by police on suspicion of murder after three young children were found dead at a house in south London.

The 42-year-old is suspected of killing a four-year-old girl and twin boys, aged three, who are all said to have suffered from a life-limiting genetic condition.

It is understood the three children were cared for full-time by their mother Tania Clarence, while their father Gary worked as a director at City bank Investec.

Police were called to the large semi-detached home in New Malden, where they found the bodies on Tuesday night.

A Scotland Yard spokesman said the woman was taken to hospital for treatment to minor injuries before being discharged and arrested. Officers are not looking for anyone else in connection with the deaths.

The family, who are originally from South Africa, moved to the wealthy suburb around a year ago and carried out a major refurbishment of the home, which included installing a lift.

A neighbour, who did not want to be named, said the three children were suffering from genetic disorders – believed to be life-limiting. An elder child, thought to be around seven or eight years old, was also living at the house but was in good health.

She paid tribute to the family, describing them as “really, really lovely people”, and said the parents are “a very, very lovely couple” who doted on their children.

She said: “They are very nice people and very, very decent. She is such a lovely person – her life revolves around the children.”

The family are understood to have also received help from a nanny and carers.

Retired nurse and health visitor Joy Devis, 86, said the news of the deaths was a “huge surprise and shock”.

She said: “They are a delightful couple, they seemed to be very happy. Their children were super, lovely children. They were very happy, there was a very nice atmosphere there.”

They are a delightful couple, they seemed to be very happy

Ethel Winstanley, who lives opposite the couple, said she met them last summer and congratulated them on the “transformation” of the house in Thetford Road following its refurbishment.

She said: “We went across to say ‘Congratulations, you have made the street look wonderful’.”

Another neighbour, who did not want to be named, said she met the couple a fortnight ago at a barbecue in the neighbourhood.

She said: “They were very friendly. He played golf and he had been playing golf that morning. He was going to America for a golf championship, to watch. We were out last night dancing and when we came home there were police cars and ambulances outside.”

Mr Clarence, who trained as a solicitor before going into banking, was not at home at the time of the deaths but is understood to have been informed about the tragedy.

Investec Bank, where Mr Clarence works as the director of investment banking for healthcare, said in a statement that the firm’s thoughts are with him.

It said: “Gary Clarence is a valued colleague and has worked with us for many years. We do not know the facts at this time but our thoughts are with the Clarence family. We are doing all that we can to help Gary and his eldest child and ask that their privacy is respected.”

Police have not given a cause of death for the three children, but said post-mortem examinations will be carried out in due course.

A poignant makeshift memorial of two teddy bears, bouquets of flowers, pot plants and a child’s skipping rope were laid on the driveway of the house by a police officer.

Uniformed officers were standing guard on the doorstep while scene-of-crime officers were seen leaving the property carrying evidence bags.

Police said they are trying to speak to members of the extended family to find out what happened.

Mr Clarence has worked at Investec, an international banking and asset management firm, for 15 years.

According to the company’s website, he specialises in healthcare and leads a team advising clients on buying and selling companies, raising money and strategic reviews.

A Scotland Yard spokesman said: “A 42-year-old woman has been arrested on suspicion of murder and remains in custody. We are not looking for anyone else in connection with this incident.”