He is described as being 6ft 1ins tall, of heavy build, with grey/brown shaven hair. He was wearing a camouflage jacket, dark blue jeans, blue trainers and a grey t-shirt.
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Officers attended the scene where a man had suffered a head injury. He was taken to hospital where is condition is described as critical.
Walkers set out from Ipswich on Easter Monday to walk 333 miles home in memory of Lee Hope, a Firefighter from Newcastle who died last year