As a club secretary I sometimes get unsolicited mail and this ladder is a case in point - the company sent out a catalogue (presumably other club secretaries received it too) specifically highlighting a ladder of this type as being of potential interest to cavers.
I did not retain the catalogue; however my fuzzy memory recalls my reason(s) for dismissing the ladder as being of genuine use to cavers. 1) It weighs around 12-18kg, I think. 2) Although it closes down, it's still damn large (n.b. Mendip caves!). 3) I suspect grit/mud/sand will play havoc with the sliding parts. 4) It cost just under £300. 5) Stability at the base was an issue. 6) For the money you could make your own purpose built ladder in sections. 7). Can't be lowered from above due to concerns over leg placement at the base of pitches.
Mind you, at £30 it might be worth checking out.