On 26 March 1887, Campbell and Portuguese Foreign Minister Henrique de Barros Gomes signed the four-point Lisbon Protocol: Art. 1st.—A Treaty of friendship and commerce with the most favoured nation clause will be concluded and signed at Peking.
Pada 26 Maret 1887, Campbell dan Menteri Luar Negeri Portugis Henrique de Barros Gomes menandatangani Protokol Lisabon empat poin: Pasal 1.—Sebuah Traktat persahabatan dan perdagangan dengan klausa most favoured nation akan diputuskan dan ditandatangani di Peking.