A fox hunt monitor found a 2in nail embedded in a Mars bar and placed in front of one of her car tyres.

Helen Ghalmi, from Protect Our Wild Animals (POWA) was filming the hounds of the Heythrop Hunt in Milton, near Deddington, when she noticed a woman near her car.

On closer inspection, she saw a sharp nail had been pushed into the chocolate bar and laid in front of one of the tyres of her Honda CRV.

Mrs Ghalmi, of Radley, near Abingdon, said: "This woman had been following me in my car and at one point even came up to me and photographed me.

"I knew something was wrong when I had pulled over to film the hounds and this woman appeared near my car.

"She had her foot near one of the tyres and was kicking something underneath the car. I pulled the Mars bar out and the woman tried to grab it off me.

"I pushed her away and she jumped in her car and drove off.

"It's very hard to say how I felt. It was the first time that I had been involved in an incident and I suppose I felt quite scared."

A 43-year-old woman, who has not been named, was arrested by police on January 23 and admitted attempting to cause criminal damage. She was issued with a formal police caution.

There is no suggestion she was involved with the hunt.

A Thames Valley Police spokesman said: "We can confirm that the woman had been arrested and admitted the offence and was issued with a caution that will remain on record for five years."

Liz Wills, joint master of Heythrop Hunt, said: "Criminal damage is something I don't condone and I am sorry it happened.

"It is not something that we would be proud of, but it shows the frustration the supporters feel by constantly being monitored. They are continually at our shoulders.

"What we are doing is legal and our supporters feel very strongly about this. Why we can't just be left alone, I don't know."

Mrs Ghalmi added: "I was very pleased with the prompt action of the police.

"I hope it deters hunt supporters from behaving in such a dangerous and childish manner."