Detective Superintendent Nick May from Surrey and Sussex Major Crime Team said: "We need to know the origins of this hammer.
"Do you recognise it? We need people to check if they have lost such a hammer or had one stolen in the period leading up to the murder.
"We would also ask police officers, prison staff, probation officers and professionals who work in mental health, if they have dealt with anyone who has talked about causing someone harm with a hammer, to let us know.
"If so we would like to hear from you. We are continuing to appeal for any information from anyone who saw anything suspicious in the area from late afternoon on Sunday 29 December to 10am on Monday 30 December to come forward."
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Dry with sunny spells to start. Warm with hazy sunshine this afternoon
A dry and bright start with long spells of sunshine into this afternoon and feeling fresher
Fine this evening, then dry overnight with mist likely in places. Sunny spells tomorrow morning with hazy sunshine in the afternoon