Mindless thieves who left a fishing boat drifting with no one on board sparked a three-hour river rescue costing about £50,000.

Two coastguard crews, police, the RNLI and a coastguard helicopter were all scrambled at just after 8am today when a 20ft motor boat (pictured right with RNLI rescue vessel) was seen with the engine on going in circles.

The lock keeper at Bullnose Lock, at the entrance of Chatham Docks, raised the alarm fearing someone could have gone overboard.

The team scoured the River Medway using infra-red sensors and checking inlets to see if a body had washed up.

Finally, the mystery was solved when CCTV showed three teenage boys leading the boat out at about 6am.

Richard Rodgers, deputy station officer at Medway Coastguard, said: "They broke into the boat at Gillingham Pier where it was securely moored, stole the owner's fishing equipment then walked it down to the end of the pier with a rope.

"They then started the engine, put it in gear and let it go."

The boat's owner, believed to be in his 40s, was traced and came to Gillingham Pier as part of the search.

But until the CCTV emerged the rescuers had no choice but to keep searching, said Mr Rodgers.

"The owner was going off to get bait to take his son fishing tonight," said Mr Rodgers. "It's quite badly damaged, there's a broken door, so he can't do that now.

"You are looking at about £50,000 for the whole operation, plus volunteers' time.

"This has taken away from valuable rescue work where someone could have been in real trouble and needed our assistance, due to sheer recklessness and vandalism. It's a total waste of public money."