A relative found the bodies of John Neale, 63, and his 57-year-old wife, Pauline, at their pounds 80,000 home in Catford, south-east London, on Tuesday afternoon.
They had been repeatedly stabbed, possibly with a kitchen knife, sometime after 2pm on Sunday, the last time they were definitely known to be alive, said Detective Chief Inspector Richard Heselden, the officer in charge of the investigation.
Speaking at the house, where the couple's Rolls-Royce was parked outside, he said: "It was a dreadful attack. Both of them were stabbed several times. They tried to defend themselves. It was a fairly ferocious attack and they had little chance."
Mr Neale was found in the summerhouse in the garden, and Mrs Neale was found in the main house. They are believed to have been attacked where their bodies were found.
Police could not confirm the occupations of the couple, who have five children. But Det Ch Isp Heselden said police would be investigating Mr Neale's line of work and any of the couple's acquaintances.
The police were called in after relatives had tried to telephone the couple without success since Sunday.
Det Ch Isp Heselden said there had been no obvious signs of a theft or a break-in. "It could have been a stranger who they let into their home, though there is some evidence they were security-conscious, or it might have been someone they knew," he said.
"We are not ruling out any possible theory at the moment. The person who did this would have been heavily bloodstained. This is a quiet cul- de-sac and we believe someone must have seen this person leaving. We are appealing to anyone who knew them or saw them at the weekend to get in touch."
He would not comment on whether the knife had been brought by the attacker, nor on suggestions that Mr Neale had a criminal record.
Mr Neale's metallic blue Rolls-Royce was still parked outside the house, which had been cordoned off and was guarded by two police officers.
Roger Seaward, 30, a London Underground duty manager who lives near by, said he had only ever seen Mr Neale drive off in his car. "He seemed to have some sort of mobility impairment. He had his own disabled bay and would park his car in it and go straight into the house or drive off as he was going out.
"You would not think that a crime like this would happen in this sort of area. This sort of violent crime around here is unimaginable."
Matt Richards, 32, a company director who owns a flat in the cul-de-sac, remembered Mrs Neale as a friendly woman. "I used to see Pauline walking her dog. She was very nice and amiable and would always talk to you in the street," he said.Reuse content