We know what you're thinking, Shmoopers: any relation to Chandler Bing?
Sadly, no. But that's all right: Possession's Toby Byng has a few other things going for him instead.
Our Mr. Byng is Sir George and Lady Joan Bailey's solicitor, and Sir George turns to him once he realizes that the Ash-LaMotte correspondence might be worth a small child's weight in gold. Toby is committed to looking out for Sir George's interests, but he's also good friends with Euan MacIntyre, and he knows—thanks to Euan's own work on the case—that Maud Bailey may actually be the rightful owner of the Ash-LaMotte letters. Luckily for the novel's heroes, Toby has no intention of trying to stop Maud from learning the truth.
Like a few other minor characters in Possession, Toby's purpose is purely utilitarian. By arranging things so that Sir George is represented by someone who just so happens to co-own a racehorse with Euan MacIntyre, who just so happens to be pursuing Roland Mitchell's ex-girlfriend, A. S. Byatt makes sure that she can bring multiple storylines together very quickly when the time comes.