The new information came from a national appeal made by Mr Charkaui's family on the BBC Crimewatch programme on Tuesday night.

During the programme, DCI Karen Trego, the senior investigating officer, announced Thames Valley Police were offering a £10,000 reward for any information that would lead to the arrest and conviction of the killers.

DCI Trego said: "I was really encouraged by the response following Crimewatch and we have had a large number of calls, of which two are particularly significant and are currently being followed up."

"We believe there are people in Aylesbury who know who is responsible and this could encourage them to talk to us and help get a conviction for the Charkaui family," she added.

Anyone who may have seen anything suspicious in Dunsham Lane in the evening on March 12 is asked to phone Aylesbury Police Station on 0845 8 505 505 or, if you don't want to talk to police or give your name, call the Crimestoppers charity on 0800 555 111.

You can also give information to the police in person by visiting any police station. To find out the opening times and location of your local station please call 0845 8 505 505 or visit: www.thamesvalley.police.uk/bcu/buckinghamshire/bcu-info/stations.htm