War memorials are to be given invisible security markings to deter the return of metal thieves.

Sutton Council has decided its memorials should be forensically marked to stop them becoming further targets for criminals, after 14 brass plaques commemorating Sutton’s war dead were stolen from Carshalton war memorial last month.

The theft came as it emerged nationally at least one wartime monument is being targeted every week because of the rising price of metal.

Police believe the plaques were stolen from the Carshalton war memorial to be melted down for scrap.

The metal plaques on Sutton, Belmont and Cheam war memorials will now be marked with SmartWater - an invisible liquid which only be seen under UV light.

It means if the metal was stolen but recovered by police, or checked by scrap dealers, it would be clearly identifiable.

The markings will be added as part of a campaign, In Memoriam 2014, by the War Memorials Trust to improve memorial protection.

Councillor Graham Tope, executive member for community safety, said: “I know the whole community was appalled by the attack on Carshalton War Memorial, which showed a complete lack of respect to those members of the armed services who have paid the ultimate sacrifice when serving their country.

“This initiative should give our war memorials added protection and I hope it will help bring the despicable thieves who target such landmarks to justice.”

Nancy Treves, from the trust, said: "We are very saddened by the recent increase in theft of war memorials. The loss of metal, particularly name plaques, is an attack on our national heritage and shows a lack of respect for the brave acts commemorated."

The Carshalton war memorial will have its plaques replaced with new ones made of Portland stone, because it is too risky to replace them with metal.

The Sutton memorial was marked with the SmartWater yesterday.

Other war memorials in the borough which people want to protect can be registered at inmemoriam2014.org.

Sutton Council has called for a change in the law to combat the problem of metal theft.

It wants to make it a legal requirement for scrap metal dealers to record and check the details of all sellers and to axe cash payments.