Is he / she mad ? F to JNB ! I'm sure you won't be short of volunteers to help you out, if required .

As far as I'm aware, it is possible to change the companion voucher name (change fee likely) - but not the holder of the voucher who must travel but you'll know that anyway. Probably a call to Amex / BA to clarify the position - please share the official response as I'm sure it's one of those questions we would all like a definitive answer to.