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.
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The London mayor publicly backed defeated candidate Owen Smith in the contest which saw Mr Corbyn re-elected party leader.
Police described it as a "growing sink hole" and it's unclear when the road will reopen.
The victim, in her 30s, was sitting in a garden in the early hours of the morning when a man leapt over the fence.