Police have arrested a man over the disappearance of the missing elderly campers who vanished nearly two years ago.
Mr Russell Hill, 74, and Ms Carol Clay, 73, have not been seen since sneaking away for a trip to Victoria's remote Wonnangatta Valley on March 20, 2020.
The man is reportedly being interviewed by Victoria Police.
It comes after new details emerged in the suspected murder of Mr Hill and Ms Clay as it is revealed their killer may have spent many hours trying to drive out of the rugged terrain with their bodies.
Detectives believe the pair were attacked between 6pm and 11pm during a random confrontation with another camper who then torched their campsite to cover their tracks.
Russell Hill (pictured, left) and Carol Clay (right) are believed to have been murdered during a camping trip
Witnesses have reported seeing a vehicle doing a 20 tp 30 point turn near the Wonnangatta track before turning around. A blue Nissan of interest to the investigation was captured hours later driving near Mount Hotham
Investigators have been examining a number of vehicles spotted in the region around that time and have zeroed in on a mid-1990s model Nissan Patrol towing a trailer - which was captured on CCTV - as holding the 'key' to the puzzle.
Now, witnesses have come forward with new information that sheds light on just how difficult - and dangerous - it would have been for the killer to flee the high country on the night the lovers vanished.
A motorist, believed to be towing a trailer, was seen driving erratically around midnight after reaching a closed gate on a narrow stretch of road north of the campsite, the Herald Sun reports.
Finding the road unalterably blocked, the driver - who was heading towards Myrtleford - performed a 20 to 30 point turn with a trailer on the narrow road and then turning to go back the way the car had come.
Hours later, the Nissan Patrol was snapped by a roadside security camera 60 km away on the Great Alpine Road at Mount Hotham just after sunrise.
Police are yet to formally reveal whether the two incidents are linked - and if the vehicles seen are in fact the same.
If so, the driver would have required considerable expertise of the area to navigate the perilous journey between the two locations.
The drive between the sightings would have involved tricky driving routes on challenging remote tracks that zig-zag through the region.
Police revealed earlier this month the Nissan was central to the investigation because painstaking video analysis has managed to account for every car exiting the remote valley that weekend - except the blue 4WD.
The mid-1990s model Nissan Patrol (pictured) is now central to the investigation because painstaking video analysis has managed to account for every car exiting the remote valley that weekend - except the blue 4WD
The 4WD (pictured in a police sketch) has roof racks, side steps, off-road tyres and a bulbar. The box trailer is 'fairly standard' but has been fitted with 'off-road wheels'
'Throughout our extensive and significant investigation over the last 20 months, we have not been able to eliminate this blue four-wheel drive from our enquiries,' Inspector Andrew Stamper said in a public alert.
'We have witness statements that put this blue vehicle and its trailer in the valley at the time Russell and Carol were there, and indeed near the spot that they had set up their camp.'
The 4WD has roof racks, side steps, off-road tyres and a bulbar. The box trailer is 'fairly standard' but has been fitted with 'off-road wheels'.
From the earliest stages of the investigation detectives had wondered why the couple set up their campsite away from the river.
Inspector Stamper now believes it's because somebody else was already camping there when they arrived.
A witness reported seeing a vehicle which matches the Nissan Patrol's description parked near their campsite on the night they went missing.
Another recalls hearing it leave the area around midnight and getting stuck on a closed road before turning around.
The pair went missing in the Wonnangatta Valley, more than 200km north east of Melbourne
Mr Hill's white Toyota Landcruiser (pictured) was found with minor fire damage at their burnt campsite near Dry River Creek Track in the valley on March 21
The leading theory now is that there may
