From The BBC
A man has been arrested on suspicion of murder after a policeman died on duty in north-west London.
The 48-year-old police officer collapsed trying to arrest a man following a domestic incident at Brinkburn Gardens in Wembley.
Police were called to the address at about 1745 GMT on Boxing Day.
A post-mortem examination will be carried out later to establish the cause of death. The man arrested is in his 30s.
Other deaths
Home Office minister Tony McNulty said: "I am deeply saddened to learn of the death of a police officer while on duty with the Metropolitan Police.
"Events such as this highlight the dangers that our police officers face every day when protecting the public."
The Association of Chief Police Officers also offered its condolences.
Two other police officers have died on duty this year.
On 6 May Pc Richard Gray was shot by a man after attending a domestic incident in Shrewsbury. The man then committed suicide by shooting himself.
In June 36-year-old Pc Jonathan Charles Henry was fatally stabbed in Luton. A man is awaiting trial accused of his murder.
My sincerest thoughts and condolences go out to our colleague's family and friends at this difficult time.