A trio of teenage boys who broke into a gym damaged a vault used in the London Olympics and scrawled crudely drawn penises on tables.

It is understood they either abseiled or jumped from the viewing gallery on to a specialist air track 9ft below to gain entry to the gym at Tenterden Leisure Centre that is used by the Kestrel Gymnastics Academy.

Leaders of the gymnastics group, which is based and trains at the leisure centre, have reported the incident to police, but have taken the unusual step of asking the three boys, who are thought to range in age from 14 to 16 years, to own up and apologise for the damage they have done.

A post on the gym’s Facebook page said: “Very sad we had 3 boys let themselves into the hall and seemed to think it was funny to use the gym equipment and also do some other bits that I cannot mention.

"Just to point out to them this is called criminal damage and you have been caught on CCTV. Do the decent thing and come in and apologise or we will take this matter further.”

Gary Crawford, the Kestrels’ head coach, said: “The boys came into the leisure centre earlier on asking about gym lessons for a younger sister, which seemed strange at the time.

"I think they got into the gym after I had finished clearing away from a cheerleading class that ended at 8pm.”

Mr Crawford, 45, said the young vandals damaged gym mats, rifled through storage cupboards containing valuable equipment, and ripped the cover of a £2,000 vault that was used in the London 2012 Olympics, making it potentially unusable for his gymnasts who are training for regional competitions.

He buys ex-Olympic equipment and owns a pommel horse believed to have been used by Olympian gymnast Louis Smith, as well as a beam from the 2010 World Gymnastics Championships.

He said: “This equipment comes with the chalk handprints still on it from the gymnasts who have used it and has so much history.

"The boys drew pictures of men’s genitalia in permanent marker on the tressel tables at the front of house, which are used for registering pupils and would be seen by our pupils, some of whom are just five to six years old.”

Mr Crawford said the boys had hooked strong ties, used for bundling up equipment, to the viewing balcony and had either abseiled or jumped down a 9ft distance on to a specialist air track in their trainers.

After Mr Crawford’s appeal, a 16-year-old boy came forward to say that he was one of those responsible for the damage during last Friday's rampage.

Mr Crawford, who had to spend an entire day clearing up, including scrubbing the penis drawings from the table, said: “I got the boy to help put away equipment and asked him to roll up the air track, which he couldn’t move, as it was so heavy. I wanted to teach him respect for the equipment.”

He said the gym was trying to secure its own premises to offer gymnastics to a wider group, incorporating freestyle gymnastics, free-running and parkour.

“I want to give these teenagers something to do and keep them off the streets,” he said.