The Duchess of Cornwall heard about the growing problem of military memorials being wrecked by metal thieves as she visited the Royal Artillery Memorial.
Camilla marked the structure, at Hyde Park Corner, in central London, with SmartWater as part of a national campaign.
The duchess was attending as patron of the War Memorials Trust.
In Memoriam 2014 is a partnership between the trust and the SmartWater Foundation to provide greater protection to war memorials across the UK.
Each sculpture and plaque on the memorial will be forensically marked with SmartWater, assigning them with a state-of-the-art forensic signature that can only be seen under UV light.
In Memoriam 2014 is offering SmartWater free of charge to the custodians of the estimated 100,000 war memorials across the UK.
The initiative was launched to coincide with the forthcoming centenary of the First World War.
War Memorials Trust director Frances Moreton said: "War Memorials Trust greatly appreciates the support of HRH The Duchess of Cornwall.
"In Memoriam 2014 offers a simple and free way for communities to protect their war memorials. It is stimulating a greater awareness and recognition of this unique aspect of our national heritage which will play a significant role in the next few years as the nation turns its attention to commemorating the centenary of World War One."