Fountain, who lost a promising lead recently when her wireless link went down, needs no reminding.

A new campaign to find her - launched to mark the anniversary of her disappearance - has thrown up several 'promising leads'.

But can they get out alive to pursue the promising leads?

Despite intensive research and many promising leads, an explanation has so far eluded scientists.

These two traits led her to pursue promising leads that other cavers were unwilling or unable to attempt.