Police in Britain arrested 54-year-old Zaid al-Hilli on Monday in connection with last year's murder of three members of his British-Iraqi family and a French cyclist in a secluded car park in the French Alps.

According to police the man was held in a "pre-planned arrest" in Surrey, outside London, near where the murdered al-Hilli family lived.

Zaid's brother, Saad al-Hilli, 50 was killed along with wife Iqbal, 47, her mother Suhaila al-Allaf and French cyclist Sylvain Mollier on September 5th, 2012. The al-Hilli's two daughters – seven-year-old Zeinab, and four-year-old Zeena – survived the attack.

Zaid was arrested on suspicion of conspiracy to commit murder.

"We needed to ask him questions"

Eric Maillaud, the prosecutor for the French city of Annecy, told AFP: "We felt there were enough reasons to take him into custody.

"We need to ask him questions about his schedule, his relationship with his brother and the family inheritance."

He said searches were being carried out at Zaid al-Hilli's home and the golf and leisure company where he works.

"The family connection remains the preferred line of enquiry, even if no new elements have emerged recently," Maillaud said.

Investigators have been looking at whether a possible feud over the estate of the brothers' father could lie at the heart of the case.

In an interview with Britain's ITV News recorded on Friday, Maillaud said documents found at Saad al-Hilli's home suggested the attack may have been timed to prevent him returning to Iraq to lay claim to his father's estate.

Earlier this month The Local reported that Police were looking into telephone calls to Romania made from the phone of Zaid al-Hilli.

Zaid had already been questioned at length by police over the investigation as rumours circulated in the aftermath of the killing that the two brothers has been involved in a bitter feud over their father's inheritance.

In the days after the murders Zaid al-Hilli presented himself at a British police station where he was questioned as a witness over the killings. He has repeatedly denied there was any bad feeling between him and his brother.

The prosecutor said: "There is the hypothesis, involving the family, around the father's inheritance. He didn't have a very big fortune but he had an important fortune in property and we know that both Saad and his brother wanted to recoup it at any price, which created tensions in the family.

"Based on letters we found and conversations he (Saad) had, he feared for his life.

"In these letters he expressed his worry for his life due to his desire to recover his father's fortune and the conflict it caused with his family. That fear was there."

After nine months of investigation that appeared to have gained little progress, Monday's arrest suggests police have made a breakthrough in their attempts to track down the killer or killers.

The statement from Surrey police read: "As part of the Joint Investigation Team (JIT), which was established on September 21 last year, officers from the Surrey and Sussex Major Crime Team have been working closely with the French authorities to progress a number of lines of enquiry.

"Thispre-planned arrest is a result of these on-going enquiries and any updates will be issued in due course."

In an interview with The Local earlier this year, Annecy prosecutor Eric Maillaud admitted their manhunt may never track down the murderers, but it was still too early to know.

“Of course it is possible we will never find them, but it’s too early to conclude that,” Maillaud said, back in March. “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.”

Maillaud said there were still around 40 French investigators working on the case, who regularly make trips across the Channel to liaise with their British counterparts in Surrey.

Police believe French cyclist Mollier was not a target and simply the victim of being in the wrong place at the wrong time.