Who is William Longstaff from Tai-Pan and what is their importance?

Longstaff is the British plenipotentiary in Hong Kong and in that area. He represents the British government as the Captain Superintendent of Trade in that part of Asia. He negotiated the treaty with Ti-sen that ended the war and transferred the island of Hong Kong to the British. He is involved in any of the negotiations with the Chinese that take place throughout the book. He usually consults the major traders on the issues and relies heavily on Dirk Struan for advice. He is relieved of his duties for negotiating the treaty against the orders of the government. Longstaff is referred to as "Odious Penis" by the Chinese.