Christmas might be coming early to Cravath, Swaine & Moore.

The firm took the lead Friday for British American Tobacco plc on its announcement of a nonbinding offer to buy the remaining 57.8 percent of Reynolds American Inc. that it doesn’t already own. The proposed $47 billion cash-and-stock deal could transform the tobacco industry, and it turned out to be the first of two mega-mergers for Cravath in a 24-hour period.