Suspect One: Aged between 20 and 30, around 6ft tall, athletic but stock build, with dark hair which was long on top. He had a well-groomed beard, dark skin tone and wore casual clothing. Suspect Two: Aged between 20 and 30, younger than his accomplice, and a slimmer build. About 5ft 10ins tall, clean shaven with short dark hair. He wore a white T-shirt and dark shorts.

Detectives investigating the attempted kidnap of a RAF Marham serviceman have renewed their appeals for help.

It is just over a month since the attack on July 20 at Squires Hill which occurred when the serviceman, aged in his 20s, was running outside the base.

The victim was grabbed and pulled towards a vehicle but managed to fight-off one attacker by head-butting him. The serviceman escaped when a second suspect, armed with a knife, went to help his accomplice.

Detectives have kept an open mind over the motive and a terrorist-related incident has not been ruled out.

Appeals and the release of images of two suspects resulted in around 550 calls from the public, with 350 relating specifically to the e-fit images.

Despite the response, officers have said there have been  no confirmed sightings of the suspects and the vehicle they used has not been traced. This was thought to be a dark-coloured people carrier.

A team of 50 detectives from the Norfolk and Suffolk Major Investigation Team and 10 from the Metropolitan Police Service Counter Terrorism Command, are working on the case.

Head of the inquiry, Detective Superintendent Paul Durham, said: “We are still undertaking a significant enquiry and our approach remains the same.

“I stated from the outset this would be a lengthy enquiry due to the remoteness of the location and sporadic nature of CCTV in the area. This means we’ve had to widen our search and naturally this work, when done thoroughly, takes time.”

He said CCTV footage remained a key focus point.

“Footage is being viewed frame-by-frame, that’s the level of detail we are looking at and there’s equally as much to review.

“The victim is continuing to receive support and remains off work as he comes to terms with this traumatic ordeal.

“I’m confident we will get to the bottom of this case. It’s going to be old-fashioned detective work which gets the breakthrough and that could take several months,” he added.

Appeals have been renewed for anyone driving in Marham on July 20 to come forward.

Det Supt Durham said: “We know through the CCTV work that there’s a number of people travelling in Marham on the day of the incident between 2.55pm and 3.15pm, specifically on Squires Hill, Ladywood Road and Burnthouse Road areas, who haven’t come forward.

“This could be because they didn’t see anything they felt was significant, but whether they witnessed anything untoward or not, I would urge these people to come forward with their vehicle details so we can rule them out of our enquiries.”

Anyone with information should call the team on 101 or Crimestoppers anonymously on 0800 555111.