A woman mauled to death by a dog at her Wallington home was "cheerful with a smile for everyone", according to the headteacher at the school where she volunteered.

Barbara Williams, 52, was savaged by her landlord Alex Blackburn-Smith's Neapolitan mastiff at her home in Demesne Road, Wallington on December 23.

Mrs Williams, who helped out with pupils' reading at St Elphege's Roman Catholic Junior School in Wallington, bled to death after suffering serious neck and head injuries.

She was still struggling with the dog when police arrived at the scene. They fought off the animal with riot shields before shooting it dead.

This week, the headteacher at St Elphege's, Frances Hawkes, said: "Barbara was always kind and cheerful with a smile for everyone. The children responded positively to her kindness and encouragement. She was respected and well liked by pupils and staff.”

Mrs Williams worked in a Year Two class in a voluntary capacity at St. Elphege’s Infant School for four years.

She spent two days per week at school where she listened to children read, helped with practical group work and assisted the class teacher with filing.

Meanwhile, the dog that killed her could have “snapped” because of the way it was kept, a canine behaviour expert said this week.

Police are still trying to piece together what happened in the run-up to the attack, but dog behaviour expert Sharon Bolt, 44, said: “This can happen when you have a built-up tension in a frustrated animal and they can snap.”

The owner of national dog training company Good Dogs added: “This can be when they are not looked after properly. This is a dog that needs to be well trained, and needs to be well exercised and mentally stimulated.

“They need a lot of dedication and cannot just be left outside in the back garden.”

Neighbours reported the dog was kept outside and had damaged their fences trying to jump over.

Mrs Bolt said she did not believe dog attacks were more likely with certain breeds, but with bigger and more powerful breeds, the risks were raised.

She said behaviour was linked mainly to how dogs were kept and how well they were trained.

The website for the UK Neopolitan Mastiff Club stated the dogs can be very territorial and protective.

A puppy was also living at the address, and is still being held at police kennels while investigations continue in to the attack, and conditions the dogs were kept in at the house.

Mr Blackburn-Smith, 34, was arrested on suspicion of manslaughter but bailed pending further inquiries.