An experienced cave diver died after a mystery accident on an expedition in France.

John Maneely got into trouble on a dive in a deep cave in Source du Doubs, near the Swiss border.

The 32-year-old, of Eastern Avenue, Shoreham, was wearing a large air recycler when he began exploring the cave.

Other divers had warned him the night before that it would be too big to get through some of the narrower parts of the cave system.

John Volanthen and Charles Reid-Henry, who also made the dive, returned safely.

They searched for Mr Maneely when he failed to surface. His body was found trapped under a ledge 26 metres down the main shaft to the cave.

French investigators say they have no way of knowing how he died during the September 28 accident.

A report from them read out at the inquest in Worthing said: “It seems that he could not make the return passage through the first rockfall in the cave.

“This may be because his recycler pack was too large and the other three divers had smaller recyclers.

“He may then have taken his off and started breathing with another bottle and managed to get through the narrow gap.

“The possibility is that after getting through he tried to put the recycler back on but could not do so.

“He may have tried to continue the ascent holding the air bottle under his arm.

“Matters then got out of his control and he made a very rapid ascent to where he was found.”

His father David Maneely, from Worthing, said his son “loved diving” and was a qualified instructor.

He added: “He broke his back in a motorcycle accident in 1999 and may have had problems getting the recycler back on as a result.”

West Sussex Coroner Penelope Schofield recorded a verdict of accidental death by drowning.