British police assisting the investigation into last year's murder of a British-Iraqi family in the French Alps on Monday released footage of a 4×4 vehicle seen close to the crime scene.

Detectives told BBC's Crimewatch programme that they wanted to trace the owner, whom they believe may be British, of a right-hand drive 4×4 vehicle which was spotted in the French commune of Chevaline at around 3:20 pm on September 5 last year.

Saad al-Hilli, 50, his wife Iqbal, 47, from Surrey and grandmother Suhaila al-Allaf, 74, who lived in Sweden, were all gunned down in their car on September 5th not far from the town of Annecy. French cyclist Sylvain Mollier, 45, was also killed nearby. The al-Hilli's two daughters – seven-year-old Zeinab, and four-year-old Zeena – survived the attack.

Just over six months down the line and despite dozens of detectives from France and the UK working on the case, the killer or killers have not been found.

Detective Superintendent Nick May said: "I am appealing for anyone with a right-hand drive 4X4, particularly a grey, black or dark coloured BMW X5, to cast their minds back to September last year. Were you on holiday in the French Alps at the time? Did you visit the Annecy area?

"I am particularly keen to speak to any owner of such a vehicle who visited the towns of Doussard or Chevaline on the afternoon of September 5 as they may be able to provide vital information to assist with this ongoing joint investigation.

"This location is very popular and there may have been a number of tourists staying in the local area or travelling through at that time of year.

"The timing of this sighting is clearly significant and it is important that we trace this vehicle if only to eliminate it from our inquiries.

"This was a shocking crime, and we remain committed to working with our colleagues in France to find whoever was responsible and bring them to justice," he added.

Earlier this year French prosecutor Eric Maillaud, who is leading the probe to solve the murder, told The Local it was too early to admit defeat in the hunt for the killers.

“Of course it is possible we will never find them, but it’s too early to conclude that,” Maillaud said. “The investigation is only six months old, which in terms of police inquiries is a very short period of time.”

“It’s out of the question that we will be thinking like that now.”

Earlier this month investigators were dealt a blow when a request by French judges to visit Iraq to try to find clues about Saad al-Hilli's family background was turned down by France's Foreign Ministry on the grounds of security.