AFAIK Originally there was a nylon cord there ... the other end was retained by one of the grip panels. They didn't survive well.
Dave G I tinker, therefore I'm broke!
Further, now that I've found the MCB BST ... I've recently sold my house and moved under the bridge down the road ... but I've got lots of markers.
I have no life, I'm just a dad in constant flux between baby naps and 8yr old tantrums.