Sheppey Sea Cadets could be hit with a repair bill of as much as £300 after vandals lobbed a bottle through a window at their Sheerness base.

Staff and young recruits arriving for training at the unit, which is a registered charity, discovered the damage just before 9am on Saturday.

One of the mess deck windows at the site in Barton’s Point coastal park, off Marine Parade, Sheerness, had been smashed by a J2O bottle.

It is not thought to have been an attempted burglary because the alarms inside the building, which are heat sensitive, were not activated.

The damage may have happened at any point between the last session at the site on Thursday night and when it was discovered on Saturday morning.

Commanding officer Brian Moore, who cleared up the mess with unit chairman Albert Wickenden, said: “We haven’t had any vandalism in quite a while. We had a few bits of kit nicked a few years ago but that’s it.

“Obviously it’s really frustrating. If we’ve got to stay down there it’s time away from the training.

“Also there’s the time spent clearing up all the bits of smashed glass because you have to make sure it’s safe, ready for the kids coming down to use it.”

He said the total repair bill was not yet known but it was estimated to be between £250 to £300.

Training was not cancelled on Saturday as the window was boarded up. It is due to be replaced later this week.

A police spokesman said inquiries were ongoing.

In 2013, the base was repeatedly targeted by thieves who stole about £400 worth of equipment between May and July.