Arsonists destroyed part of the award-winning nature trail at Newmillerdam Country Park on Friday night for the third time.
These dramatic shot show the firefighters battling to bring the flames under control.
A viewing platform was set alight, along with bridges and around 100m of the boardwalk.
The fire, which badly damaged dozens of trees, came almost two years to the day that a platform and 30m of boardwalk were first set alight.
It took volunteers six months to replace what was lost on that occasion so that park users of all abilities could once again enjoy the circular Lawns Dike Trail.
Friends of Newmillerdam Country Park chairman Jeff Stimpson yesterday said: “There have been three attacks and this is the worst unfortunately.
“The material isn’t flammable. It only sets fire if an accelerant is used, so someone has carried a petrol can for more than a mile.”
He said the group would reinstate the trail as soon as possible, although they were likely to look at an alternative to rebuilding the boardwalk given the risk of further damage.
Since news of the damage was shared on the group’s Facebook page, hundreds of supportive messages have been posted including offers to volunteer or donate funds.
Mr Stimpson said the response was heartening in the wake of another setback for the group’s members.
“People in the park today are incensed,” he said. “The disappointment [for us] is severe but, in a strange way, not as severe as it was the first time. You always fear this.”