They want to hear from taxi drivers and anyone out in town who saw an "unprovoked" attack at the Hamilton Terrace taxi rank, at about 12.30am on September 28.

As part of the investigation, they released these CCTV images today.

The incident left a 32-year-old man from the Chase Meadow area unconscious in the street. He suffered serious head injuries and was in a critical condition at University Hospital, Coventry for several days.

He is now said to be "improving", but will remain in hospital "for a considerable period of time".

In particular, detectives want information about three men.

Det Supt Andy Smith said: "We believe they were in the area immediately before the incident and ran off in the direction of Regent Court and into Regent Street.

"They were last seen in Park Street heading towards Warwick Street. We are keen to trace them to talk to them about what they may have seen. We are appealing to anyone who recognises their descriptions to contact us.

"If you were a taxi driver and believe you may have taken them out of town, or to an address locally, please contact us."

The first man is described as white, in his mid-20s, approximately 5ft 9ins tall and wearing a blue t-shirt with white motif on the front and jeans.

The second is described as Asian, casually dressed in a dark-coloured short-length coat with jeans.

The third is said to be a larger white man with short hair. He wore a long-sleeved dark top with a light-coloured motif on the chest, which he took off, a light t-shirt underneath and jeans.

The assault, opposite the police station, was described as "a totally unprovoked attack" by the victim's father last week. He said: "He's a married father - and not the type to be looking for a fight. He texted his wife to say he was on his way home and that was the last we heard."

Det Supt Smith added: "We believe this man may have been an innocent victim who was in the wrong place at the wrong time. We would urge any member of the public who has not yet come forward with any information that could help our enquiries to please contact us straight away."

Anyone with information should call 415000 ext 4110 or Crimestoppers anonymously on 0800 555 111.