David Letterman, 61, has finally tied the knot with the mother of his five-year-old son, Harry. He broke the news on his talk show yesterday. He and longtime girlfriend Regina Lasko, 48, married before a justice of the peace March 19 in Choteau, Montana, where he owns a ranch. Letterman told his audience: “I had avoided getting married pretty good for, like, 23 years, and I … secretly felt that men who were married admired me, like I was the last of the real gunslingers.” He related that his truck had gotten stuck in the mud on the way to the courthouse, which gave him pause to think that maybe it wasn’t meant to be. “So now we think: Well, somebody’ll come,” he said. “No, nobody … comes along. Nobody comes along. It’s Thursday afternoon, who’s coming along, Zorro? No, nobody — so I get out of the truck and I walk two miles back to the house. And the whole way, I’m thinking: See, smart ass, see, see, you try to get married, this is what happens.” However, it all went well in the end and he and Lasko were married with their son in attendance.