The culprits smashed the eggs on the nest by putting bricks on top of them on the edge of the moat at Whittington Castle. Just one of six eggs survived.
Police today appealed for anyone with information to come forward, including those who might have CCTV footage of the castle on Wednesday night.
Villagers have set up a Just Giving site to fund more CCTV cameras. Last year they raised thousands of pounds to pay for specialist cleaning of the castle walls after obscene graffiti was sprayed onto the historic stonework.
They say the latest attack is the lowest blow for the castle.
The vandalism was found by mother and daughter, Terri and Stephy Wilson walking their dog, Heidi, past the castle at about 6am yesterday .
Stephy said they have enjoyed seeing the pair of swans build the nest and tend the eggs over the last few weeks.
Appeal. Overnight the eggs in the swan's nest on the moat at the castle have been destroyed. If you have any information please call 101 quoting 0260s 250419.— Oswestry SNT (@OsCops) April 25, 2019
They could not believe it when they saw three bricks on the eggs.
"Someone in this village is truly heartless," she said. "All but one egg had been crushed.
"It really was heartbreaking, the swan let us climb over the rails to move the bricks, she just watched us.
"After we moved the bricks she started clearing the crushed eggs off the nest it was so sad."
The vandalism has shocked the village with people taking to facebook to express their disgust.
One supporter of the castle, Gareth Owen, has launched a social media appeal to raise money for additional CCTV cameras at the castle.
Others have volunteered to act as informal wardens to keep a watch over the nest in the hope that the swans will carry on sitting on the remaining egg.
Castle manager Sue Ellis said:"It left us completely speechless. We love the swans here and this beggars belief. How on earth can someone even think of doing this.
"Local schoolchildren, who named the swans, Beatrice and Benedict, have been keeping an eye on them making the next and laying the eggs, they will be heartbroken."
She said that there was an outside chance that swans could produce more eggs.
"It is only an outside chance though," she added. "We are not sure whether the surviving egg will be viable now as unfortunately the female has not been sitting on the nest much since the attack."
This weekend sees a major re-enactment event in the grounds of the castle, based on the Napoleonic Wars.