Speaking to The Bucks Herald Detective Chief Inspector Karen Trego said that there have been more than 1,000 separate lines of inquiry with statements from 600 people and police have viewed more than 500 hours of CCTV footage as part of their investigation.

Mr Charkaui was murdered in his home in Dunsham Lane on March 21 after being hit on the head with a spade.

In May a £10,000 reward was put up for information leading to the arrest and conviction of the people that carried out the attack and the case featured on BBC Crimewatch.

DCI Trego said that a brown purse they are looking for has still not been found.

She said: "I think what it's really important to stress is that the inquiry continues and it will continue until we've exhausted all our possible lines of inquiry and we're still some way from doing that. What I do think is that ultimately somebody knows something, somebody local probably in the Aylesbury area knows something and out of misplaced loyalty, which could be for any kind of reason, they are just not talking to us.

"I would encourage that person or those people to please talk to us. We do need to hear what you've got to say. We've still got lots of bits of our jigsaw that we need to put together and we can't do that where we are at this time."

She added: "It's a complex investigation. Clearly we've got to methodically go through the evidence that we have got, seek further evidence and continue with the investigation.

"It's not being scaled down, it does still continue with a number of officers dedicated to it and police support staff and forensic work which still continues and that will go on for several months at least as I anticipate it at the moment.

"There may come a time, and it wouldn't be right for me to try and speculate when that might be, when all possible lines of inquiry have been carried out and we will then have to review the situation, but as I say, we're still some way from that yet."

If you can help with the inquiry, call Aylesbury Police Station on 0845 8 505 505 or call the Crimestoppers charity, anonymously, on 0800 555 111.