A SEA King helicopter was spotted today (Tuesday) hovering above Darent Valley Hospital, but the distress signal it was responding to turned out to be a false alarm.

A spokesman for the Gravesend RNLI admitted they had no idea what set off the Epurb, a satellite-guided safety beacon triggered when boats sink.

The RNLI was first called out after the Epurb warning at 10am.

When lifeboats could not locate the source of the signal they called in the Sea King 125, a search and rescue helicopter based at RAF Wittering, in Peterborough.

The aircraft has specialised locating equipment and found the signal at Darent Valley Hospital, but the RNLI said they did not know what set the signal off.

An RNLI spokesman said: “The Epurb had been activated by mistake and the distress signal was found near the hospital.

“We don’t know what set it off.”

The RNLI returned at just before noon after the Epurb was located.