A memorial stone laid by Britain's last survivor of the World War One trenches, Harry Patch, has been stolen from a plinth in Belgium.
Mr Patch, who died in 2009 aged 111, was the last surviving British soldier to have fought in the conflict, and was present at the unveiling in 2008.
RAF Air Cadets visiting the 6ft (1.8m) memorial found it missing on Tuesday.
Police in Belgium said officers were investigating the theft of the plaque.
Chief Commissioner Georges Aeck, from Ypres Police, said: "We have been informed of the theft of the plaque on the 12 of July. We have started an investigation but so far without any results."
The Commonwealth War Graves Commission said it was aware the stone was no longer in place.
Peter Francis, from the commission, said if it had been stolen the person who had taken it "should be deeply ashamed of themselves".
"It beggars belief that someone would take a memorial to a man who typified the service and sacrifice of millions of young men during the First World War," he said.
Despite an appeal for information and a police investigation, the memorial's whereabouts and condition is unknown.
A crowdfunding appeal to replace the stone, which went missing on 11 July, reached its target of 1,500 euros in less than five hours.
Simon Louagie, education officer at nearby Peace Village which houses an estimated 25,000 guests who visit the battlefields every year, met Mr Patch when he was 16.
"Harry made a very big impression on me which got me involved in this job," he said.
"He would be very sad and shocked to know it had gone but equally very happy it was being replaced as a memorial to his comrades so quickly."
Mr Louagie said a local stonemason would be commissioned to make a replacement.
Nick Tolson, chairman of the 914 (Glastonbury and Street) Squadron, said Mr Patch, from Combe Down, near Bath, would have been "absolutely gutted" at the news.
His wife Alison, who is officer-in-charge of the Squadron, had gone out with 10 to 12 cadets to visit the Langemarck area and planned to clean the memorial.
But when they arrived on Tuesday there was a sign next to it appealing for information.
"Alison promised Harry face-to-face that she would look after the memorial," Mr Tolson said.
He added: "It marked the point where he crossed the Steenbeek brook in 1917 where three men were killed and Harry was injured before the attack on Langemarck.
"The stone was paid for by Harry and he organised it. Harry would be absolutely gutted, he was such a peaceful gentleman."
Langemarck is the site of one of only four German cemeteries in the western Flanders region of Belgium with more than 44,000 soldiers buried there.
The village is about six miles (10km) north of Ypres where hundreds of thousands of soldiers lost their lives in World War One.