"Taxes, fees and surcharges do apply to the companion as well as the travelling card holder. The card holder will pay the cash supplement assessed for him/herself and all others in the booking, using the credit card associated with the voucher."
Can we clarify this one? It consistently seems to come up as a question - and I don't think this is completely true.
It's pretty much conclusively confirmed now that (for online bookings at least) that any Amex card can be used to pay the associated fee's and taxes. It does not have to be the BA American Express card the voucher was earned against. The booking does require an Amex card be entered, but the online form does not have the ability to distinguish one Amex card from another...