Given the question: Facts: - department: metropolitan police service - death date: 6 july 1940 -lrb- aged 28 -rrb- - name: jack william avery - death place: st. mary 's hospital , london , england - badgenumber: 890a Based on these bullet points, write a short biography describing the life of death of jack avery .
The answer is:
jack william avery was a war reserve constable who was murdered in hyde park , london , on 5 july 1940 , having served less than one year with the metropolitan police service .avery was stabbed in the groin by frank stephen cobbett , after avery approached him having been advised by a member of the public that cobbett was acting suspiciously .cobbett , then aged 42 and of no fixed address , was originally sentenced to death for murder , but after an appeal served 15 years penal servitude for manslaughter instead .in 2007 ian blair , then metropolitan police commissioner , unveiled a memorial to avery in hyde park , close to the place where he was attacked .