Was Brit Rolls-Royce designer targeted? Mystery over killing of 74-year-old as it's revealed knifeman rang doorbell to lure him out of German home before stabbing him and cut CCTV cables - as manhunt continues

Questions continue to mount around sudden killing of a top British Rolls-Royce designer at his home in Germany with police chasing new leads to help catch the unknown assassin.

Ian Cameron, 74, was discovered at his £3,000,000 home in Lake Ammersee in Upper Bavaria on Friday evening, with local media reporting he had been stabbed by a man. 

Investigators now believe the elusive assailant rang the doorbell to Mr Cameron's home and attacked him when he opened the door, forcing wife Veronika Kloos to flee to safety over a wall.

Suspicions were raised that the designer was deliberately targeted when it emerged the cables to CCTV cameras over the garages where his high value cars were kept had been cut.

Police have made swift progress in their manhunt, drawing on witness testimonies and footage from a supermarket that they believe shows the killer shortly before the murder.

'We are following all possible leads and are confident that the suspect will be apprehended soon,' said a police spokesperson. 

Some 30 officers have been deployed to assist in the ongoing hunt for the attacker, whose motives remain unknown.

Neighbours provided a description of the perpetrator which police will compile with other emerging evidence.

They recalled that the suspect was between 1.80 and 1.90 meters tall (5ft 9" - 6ft 2"), wearing light-colored trousers and a dark blue hooded sweatshirt.

Before the crime, the killer is said to have been shopping in the Edeka supermarket on Seestraße.

Surveillance cameras caught the suspected perpetrator at the store, just 0.8 miles from the designer's house, shortly before the attack took place.

CCTV footage emerged of the killer in the supermarket shortly before the killing carrying a red rucksack and green-yellow gloves.

After police sent drones and even a police helicopter to search for the murderer, they found the rucksack which is now being analysed for usable DNA traces, a crucial step that could provide a breakthrough in the case.

Super-recognisers, specialists with the ability to recognize faces even in poor-quality images or when perpetrators wear masks, are also now being brought in to help ID the suspect.

These experts need a comparative image from a recognition procedure to identify the killer.

The investigation team has now extended the manhunt to the whole of Germany.

Officials hope that new evidence from the red rucksack and CCTV footage will soon lead to the arrest of the perpetrator. 

Despite the developing leads, the search had initially faced setbacks.

Due to heavy rain on Friday evening, the police helicopter could not take off immediately, leading the search to be conducted with drones instead.

The day after the crime, divers and dog handlers scoured the area, so far without success.

Police understand that the killer rang the doorbell of the house in Herrsching am Ammersee before attacking him on Friday evening.

When Cameron opened the door, the stranger attacked him.

Cameron's wife fled over a wall to evade the attacker and finding refuge with neighbors who called the emergency services. 

A short time later, the designer was found dead.

Investigators discovered that the CCTV cameras above the garages to the house had been disabled by cutting the wires.

An officer told The Sun it is 'extremely rare' that a burglar who prepares enough to disable CCTV then 'stabs and kills' a person.

Police labelled it a 'violent crime' and said the attacker fled on foot from the house. 

Ian Cameron was a revered figure in the automotive industry, having left a lasting legacy at Rolls-Royce with his groundbreaking designs.

Before retiring from the company in 2013, he was championed for his work on luxury cars including the 3 Series, Z8, Phantom, and Ghost. 

His untimely death has shocked the small, otherwise idyllic community on Lake Ammersee.