A man in his 60s has been arrested in connection with the murder of a retired colonel on the doorstep of his home.
Lt Col Robert "Riley" Workman found dead on his doorstep.
Lt Col Robert "Riley" Workman, 83, was shot on 7 January at Furneux Pelham in Hertfordshire.
A man from East Hertfordshire was arrested after he refused to give police a taped sample of his voice.
A mystery 999 call asking for an ambulance had been made from a telephone box in a nearby village on 8 January at 0500 GMT.
The man was released on bail and police say their inquiry is continuing.
The case has been publicised on the BBC Crimewatch programme and several appeals for information have been made.