Officials at Suffolk's nature charity admitted they were "devastated" after a blaze destroyed a viewing platform at a popular nature reserve.
Firefighters spent more than two-and-a-half hours tackling the blaze at Oulton Marshes in Lowestoft.
Two crews from Lowestoft South fire station responded to reports of a blaze at Fisher Row, off Church Lane in Oulton Broad at 1.53pm on Sunday, June 12.
A Suffolk Fire and Rescue Service spokesman said the scene had been cleared by 4.26pm.
Carlton Marshes, together with Oulton Marshes, is a lowland reserve in the Broads National Park, which has benefitted from a transformation of about 1000 acres of wildness after National Lottery Heritage Fund's investment of more then £4 million.
With Carlton and Oulton Marshes separated by Oulton Dyke, the 151 hectare nature reserve in Lowestoft is managed by the Suffolk Wildlife Trust.
As Oulton Marshes is situated on Church Lane, Oulton Broad, the charity believes the blaze started at "some time over the weekend" - with charred remains now all that is left at the site of where the former viewing platform that was popular with visitors used to be.
Matt Gooch, the North East sites manager at Suffolk Wildlife Trust, said that "irresponsible behaviour" had tarnished the investment that has been made in the transformation of Carlton Marshes - and they are now struggling to get the popular platform replaced.
Mr Gooch admitted the North East Suffolk team at the county's nature charity had been left "devastated" by the weekend's blaze.
Hitting out at those responsible, Mr Gooch said: "This was where the viewing platform used to be at Oulton Marshes before some lovely person decided to set it on fire this weekend.
"The team here are devastated at the irresponsible behaviour of using a disposable barbecue in the countryside and it highlights that people need to ensure they are disposed of properly.
"This is thousands of pounds of investment for the enjoyment of visitors to Oulton Marshes."
The charity has urged anyone with information about those responsible, or if you can help with funding, to contact them.
Mr Gooch added: "Unfortunately we are going to struggle to get this replaced unless funding can be sorted externally - really disappointed."
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