A father-of-two who confronted a burglar in his house was stabbed to death as his children slept.
Robert Symons died in hospital
Robert Symons, 45, was attacked by an intruder on the ground floor of the house in Chiswick, west London, early on Wednesday morning, police said.
Mr Symons, a teacher, was found with stab wounds by his wife and was taken to hospital where he later died.
Det Ch Ins Steve Morris said "This was a callous murder of a respectable man woken by an intruder in his home."
Police said despite a forensic search of the area, no murder weapon has been found.
Friends paid tribute to Mr Symons, with one saying: "He was very gentle, very nice and always had a friendly word for the neighbours. They were a respectable and intellectual couple."
Another neighbour added: "I can't think of anything like this happening here before but the area has become a lot rougher in the last five years."
Police said a man seen leaving the property was wearing a light-coloured short sleeved shirt and may have had an accomplice.
A post-mortem examination will be held at Fulham mortuary on Thursday.