Crematorium managers are coating metal memorial plaques with an invisible liquid to thwart scrap thieves.

Oxford Crematorium has been plagued by thieves taking plaques to sell to scrap dealers - just days ago one was taken from the grave of former union shop steward Martin 'Nod' Morley.

Now the crematorium, in Bayswater Road, Headington, is using a substance called Smartwater, an invisible liquid which stains thieves' hands and clothes.

Manager Trish Smith said: "This acts as a strong deterrent to crime in our grounds, giving comfort to families that the memories of their loved ones are safer."

Police believe the bronze plaque on Mr Morley's grave, which cost £800, was prised off its mounting some time between 8am and 4pm on Monday.

Mr Morley, of Sadlers Court, Abingdon, was a shop steward at the BMW Cowley car factory, who passed away on New Year's Day.

His widow, Anne Morley, 53, said: "It's just so distressing. I don't know why anyone would do such a thing.

"Don't they realise that we've been through enough? Nod only passed away in January and this is just another thing to get through.

"It would have been Nod's birthday in a few weeks and I wanted the plaque there for that, so people could go and see it and pay their respects - now it's gone.

"I know what I would like to do with them if I found them."

Though Mr Morley's plaque was the only one taken this week, police are investigating if the theft is connected to other incidents where metals have been stolen in the county.

Last September, about 200 plaques were stolen from the crematorium in an overnight raid and over the past 12 months, there have been at least 2,000 reports of metal thefts in Oxfordshire, ranging from old cars to lead stripped from church roofs.

Mrs Smith said: "We have ordered a new plaque and trust that this will bring some comfort to his widow. Mr Morley's new plaque will be treated (with Smart- water)."

Det Sgt Gavin Collier said: "There's currently a massive market for scrap metal, which is why we have seen a rise in this type of theft. The use of Smartwater is definitely the way forward in preventing this and is a massive deterrent to thieves."

Anyone with infomration should call Oxford police on 08458 505505.

Smartwater is a liquid invisible to the naked eye that only shows up under ultra-violet light.

Each bottle has a unique code registered to the premises where it is used, helping police to link thieves to crime scenes.

Once the liquid comes into contact with people's skin it can remain for up to a month and even longer in the case of clothing.

The majority of police forces across the country now carry out checks for Smartwater on criminals to link them with thefts.