Despite being twice warned by senior staff after allegations of inappropriate behaviour Charles Ellis – a former keeper at Chester Zoo – continued touching young girls until one victim finally revealed to police what had been happening.

The 60-year-old was convicted of ten offences of sexual assault on six girls – which happened at a primary school in Wirral – after a trial during which he denied all the allegations.

Judge Thomas Teague, QC told Ellis how he had read letters revealing a positive side to his character but added: “Nevertheless the case remains serious because of the element of a breach of trust and the indictment covers a course of conduct over about eight years.”

He told Ellis, of Oakfield Drive, Upton, Chester: “This case is a tragedy for your victims, for yourself and for your family. For those consequences including the loss of your career and good name you are solely responsible.”

He pointed out that the charges involved multiple incidents representing a course of conduct against girls aged about eight and nine whose “parents had entrusted them to your care.”

Judge Teague said that the offences committed by Ellis, who was a form teacher but also taught German, generally occurred in the classroom. “You would put your arms around girls when explaining pieces of work and exploit that opportunity to touch them.”

Charlotte Kenny, prosecuting, told Chester Crown Court how Ellis had been employed at the school since 2002 and the offences began a number of years later and spanned eight years.

During his trial last month, which took place in Liverpool, she said that Ellis had been “motivated by sexual gratification” and was “a man who appears not to be able to control himself.”

The jury heard how one of the victims complained to her mum about his behaviour after which he was spoken to by the school head but no action was taken against him and he continued with his conduct.

At one point a colleague saw him touching a girl in a manner which made her uncomfortable and reported him to the deputy head mistress but he was simply given training and warned not to be alone with a child.

The following year she again saw him behaving in a similar way and reported him but before action could be taken the victim, whose claims led to the official investigation, had gone to the police. Ellis was suspended by the school.

The court heard that the offences involved him regularly putting his hand on the backs of victims under their clothing – several times a week over two years with one girl – putting his hand down the waistband of their knickers and touching their bottoms under and over clothing and touching their legs under their skirts.

With two of the girls, when they said they were unwell, he used the pretext of seeing where the pain was to inappropriately touch them.

Miss Kenny said that victim impact statements from four of the girls revealed differing levels of psychological impact. Although some said they had liked him as a teacher his behaviour had negatively affected their trust and confidence with male teachers.

Fiona McNeill, defending, said that Ellis had always denied there was any sexual motivation in his behaviour. “He accepted on occasion placing a hand of comfort around a child but that was the only motivation.

“He accepts that even when he acted in that way it was unwise particularly as he had been the subject of a number of warnings.”

Miss McNeill said that the defendant, who came to teaching late life, had led an otherwise blameless life in his earlier career.“He was clearly a dedicated teacher and brought an added dimension to the school.”

She said: “He has lost the career he loved and these convictions will have a long lasting impact on him and his family.”

He was the “centre of his wife’s world” and she has been receiving treatment because of the psychological impact on her.

“His incarceration will not only have an impact on him but have an impact on his wife. The loss of his good name is a severe punishment in itself.”

Ellis, who showed no reaction, was ordered to sign on the Sex Offenders Register for life and the judge imposed a Sexual Harm Prevention Order.