Nottinghamshire Police divers have helped to recover 250-year-old stone from the River Poulter after a bridge in Clumber Park was vandalised.
The dive team recovered a large amount of the stone as part of the training exercise.
This comes after officers were called at around 8am on March 3 to a report of damage to the bridge and an abandoned car.
On March 12, officers were called to Clumber Park again following a report of a fire at The Bunk House at around 12.30am.
The barn is used as accommodation and around eight people were sleeping there at the time; they were alerted to the fire by a smoke alarm and escaped uninjured.
A National Trust van was also set alight and there was a report of a separate bin fire within the grounds around half an hour earlier.
A 27-year-old man has been arrested on suspicion of criminal damage, theft of a vehicle and arson with intent to endanger life.
He has been released on police bail with enquiries ongoing.
Neighbourhood Inspector Neil Bellamy said: “It was so disheartening when Clumber Park was maliciously targeted for two weekends in a row.
“Clumber Park is a wonderful place that the local people are very fond of.
“We will continue to assist the National Trust in any way we can.”
Project lead for the restoration of the Ornamental Bridge Rob Brough said he was ‘grateful’ to the force.
He said: “The exercise has been a great success, with large quantities of stone recovered, which will now be assessed by expert National Trust stonemasons.
“We’d like to thank Nottinghamshire Police for all of their assistance and we are excited to be moving the restoration of this iconic bridge forward.”