A former school caretaker warned bosses about a predatory teacher years before he was jailed for sexually abusing two pupils, it has emerged.

Colin Mier reported Robert Appleby to the head teacher at Herne Bay High after finding him locked in a store cupboard with a schoolgirl.

An internal investigation in 2010 found his claim to be unsubstantiated, but this year Appleby, of Stablegate Mews, Canterbury, was convicted of abusing two former pupils, with sexual images of one found on his computer.

One of his victims, Georgie Childs, last month told KentOnline how Appleby had groomed her for his own sexual gratification.

Mr Mier, 68, who retired three years ago, says he is disappointed Appleby was not stopped in his tracks sooner.

“The bloke came straight up on my radar as soon as I met him,” he said.

“He always seemed to have girls, not lads, around him after school.”

VIDEO: Mr Mier talks about when he came across Appleby in a store cupboard with a student

Appleby, 42, was arrested in 2015 after former pupil Miss Childs, now 27, wrote a letter to Herne Bay High principal Dr Claire Owen, detailing her abuse at the hands of the art teacher.

A police investigation was launched, with detectives finding sexual images of a second pupil on Appleby’s computer.

The teacher was charged with a number of sexual offences, admitting those against the second pupil but denying the abuse of Miss Childs.

At his trial, the prosecution described him as a “manipulative, predatory abuser” and he was convicted by a jury.

He was later jailed for seven years and nine months, but his sentence was recently cut to six years on appeal.

Mr Mier, a former Royal Marines NCO who lives in Littlebourne, believes Appleby could have been stopped years before his arrest.

Recalling the allegation he made to school bosses, he told how he had spotted a coat and bag in Appleby’s art room as he went to lock up after a weekend fun day.

He noticed the door to a storeroom was shut and decided to investigate.

“It was just intuition and as I had a master key, I quickly unlocked the door and opened it,” he recalled.

“I saw a girl up against the wall and Appleby just threw himself back and came out and brushed straight past me.

“I didn’t see him kiss or her anything like that, but he had locked himself in the room with a young girl and to me that was enough.

“I was absolutely fuming and looked him in the eye and said, ‘you’d better get out of here’. I didn’t say anything to the girl because I didn’t want to embarrass her.

“I thought about telling the police but decided to report it to the principal, who asked an independent teacher to take a statement from me.”

Mr Mier expected action to be taken, but following an internal probe Appleby continued to teach at the school.

Mr Mier said: “Nothing happened, and when you look at it from their point of view, it’s two people’s word against mine and they said it couldn’t be substantiated.

“I didn’t speak to anyone about it for a couple of years, but shortly before I retired in 2013, I felt I had to say something to a staff member because Appleby was still teaching there.

“I said, I’m telling you this because I am retiring in April and he’s going to get away with it again. I know he’s going to do it again. But nothing happened and I thought what else can I do – it was just eating me away.”

Mr Mier said he next heard about the incident when a police officer telephoned and asked him to provide a statement about what he had witnessed.

He said: “My regret is that had the school dealt with it differently at the time, he could have been stopped there and then.”

Responding to Mr Mier’s reported allegation in 2010, the school released a statement.

It said: “Herne Bay High School acts on any allegation in full accordance with statutory guidance and Kent County Council’s protocols for safeguarding.

“As such, any allegation pertaining to a member of staff is referred to KCC’s local authority designated officer, which provides management and oversight of individual cases and guidance as to how a school should deal with the matter.

“With regard to the 2010 allegation, it was referred to KCC’s local authority designated officer, who advised the school that a full investigation was required.

“Following an assessment of the findings of the investigation, which included interviews with relevant individuals, the allegation was found to be unsubstantiated.”