Detectives are desperately appealing for information about a couple who they believe are key witnesses in the James Attfield murder case.
Officers have said is a possibility that a man and woman recorded on CCTV are the same couple seen later that evening on a bench and so become key witnesses to the murder.
James Attfield, known to his friends as Jim, was found seriously injured with over 100 stab wounds in Castle Park off Guildford Road shortly before 6am on Saturday, March 29.
He died a short time later at the scene.
The 33-year-old man from East Bay in the town was last seen in the Public House on Middleborough on Friday, March 28.
He left there shortly after 10pm, never to be seen until he was found the following morning.
Following a series of elimination enquiries, officers think that the couple pictured in image 16, shown above, are possibly the man and woman who were seen sitting on a bench at 11:30pm on Friday, March 28.
Detectives believe they had an argument earlier in the evening which accounts for why they were sitting at opposite ends of the bench.
The man is white, of stocky build and has long legs while the woman is white.
Approximately 10m away was a man sat on the grass who was white, aged in his 30s and was wearing a dark jacket and possibly jeans. There is a strong possibility that this was James.
A Crimestoppers reward of up to £5,000 still remains on offer for information which leads to the arrest and conviction of the person or people responsible for the murder.
Anyone with information is asked to call Essex Police on 101 or Crimestoppers anonymously on 0800 555111.
A man and a woman, both aged 27 and from Colchester, are currently on police bail until Friday, May 9 after having been arrested in connection with the murder.