The helicopter landed 20 yards from where the woman fell

Surrey Police's helicopter was called into action when Louise Callzetti fell down a sheer drop into the river on Thursday night.

She was in the water for more than half an hour before police and firefighters were able to pull her out using ropes.

Police said it would have been almost impossible to find her without the helicopter's thermal imaging equipment.

Ms Callzetti and her partner Jan Swift-Smith were walking with their yellow Labrador Scruffy through fields off Meath Green Lane in Horley at about 2200 GMT.

'Cliff of mud'

They told police they had walked through a field of cows and bulls when the cattle began chasing after Scruffy.

As they tried to rescue the dog, 32-year-old Ms Callzetti fell down a sleep slope into the river.

Mr Swift-Smith, 49, said: "There was no way I could get down the bank to help Lou, it was practically vertical and about a nine foot drop, which was just like a cliff of mud."

He tried in vain to attract the attention of a fire crew driving past and then ran 200 yards to a house and asked the people to dial 999.

Fears for health

He said by the time he got back to the river he could see the helicopter and waved like mad.

Officers on the helicopter used a thermal imaging camera to spot the dog running around, then found the woman in the water.

Fearing for Ms Callzetti's health as she had been in the water more than half-an-hour, the pilot landed the helicopter landed less than 20 yards from where she was.

Firefighters on the ground headed towards the aircraft and used ropes from the helicopter to pull Ms Callzetti out and she was taken to hospital suffering with hypothermia.

Police said it probably would have taken several hours to find her in a ground search as it was so dark.