The card is issued by Amex and not a bank - the only reference to terms and conditions for the night at the Ritz is the following foot note in the brochure:
"spend over £5,000 on your card in a year and get one complimentary night's stay at the Ritz Hotel Paris, in a double room (subject to availability). One complimentary night during any visit to the Ritz Hotel. Other restrictions may apply"