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.
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Union officials rejected a revised offer from Underground managers during a meeting at the conciliation service ACAS this afternoon.