Over the last few years, thieves have targeted war memorials in Enfield, Lewisham and Surrey.
Brass plaques were ripped off the war memorial in Carshalton last year, apparently taken for their scrap metal value.
They were eventually replaced thanks to a £20,000 donation from a scrap metal dealer, who had been outraged by the theft.
The garden of remembrance at Broomfield Park in Enfield was also attacked in 2009.
In total, 16 brass plaques - containing the names of 15,000 war dead - were wrenched off the walls of the monuments.
Individuals and organisations which look after war memorials are being encouraged to apply for free "SmartWater" kits.
A unique traceable liquid, which is painted onto the memorials, "SmartWater" is virtually impossible to remove - and can even withstand burning and sand blasting.
Today, the Duchess of Cornwall helped to protect the Royal Artillery Memorial on Hyde Park Corner, by applying the fluid with a paint brush.
Nancy Treves from the War Memorials Trust says that it is vital our war memorials are protected, as they provide unique records of the men and women who have made the ultimate sacrifice.
By taking a paint brush to a war memorial in Hyde Park, the Duchess of Cornwall lent her support to a new campaign called 'In Memoriam 2014'.
It aims to protect the nation's war memorials by marking them with 'SmartWater' - a traceable liquid that should deter metal thieves.
Project Manager Jon Teare explains more in the clip below.
The Duchess of Cornwall applied a traceable liquid called SmartWater to the Royal Artillery Memorial at Hyde Park Corner. The liquid is used to identify memorial plaques that have been stolen.
The Duchess of Cornwall has been meeting representatives of the Trust in Memoriam 2014 campaign at the Royal Artillery Memorial on Hyde Park Corner.
She is highlighting work done by the trust to reduce war memorial theft.
Memorial theft has been on the increase over the last couple of years as scrap metal goes up in value. The trust is trying to reduce these thefts by marking memorials with SmartWater, a liquid which leaves a traceable forensic signature.