In the context of an impending French invasion of Spain in January 1823. William à Court hailed the Spanish proposal to resolve the privateering dispute by creating a mixed commission as ‘a great point gained’. But despite these obvious political advantages, à Court expressed some reservations about whether a mixed commission could effectively compensate British merchants. The 40 million reales that the Cortes had set aside was only a quarter of the amount that à Court believed British merchants were owed, while the proposed scheme of arbitration via a mixed commission was likely to lead to immeasurable difficulties.

But such concerns were waived aside in early 1823 and the British and Spanish governments signed a convention on 12 March establishing a mixed commission to investigate British claims. This commission would comprise of two British and two Spanish representatives who would meet in London. A period of six months would be provided for British subjects whose vessels and property had been seized by Spaniards since 1808 to prepare and submit their claims. An adjudication process would follow and the claimants whose cases were approved by the commission would be paid out of the 40 million reales set aside by the Spanish Cortes. In the event that the opinions of the British and Spanish commissioners were divided regarding a specific case, two arbitrators would be consulted, and if opinion remained divided, cases would be decided by the drawing of lots.