So, i concluded that the first was David Niven, considering Sir James Bond to be the lead. But later, when I googled for info on the first James Bond, I realised that the first Casino Royale(1954) was aired in the form of episodes on CBS.
And guess who was in the lead? Not David Niven, nor Sean Connery. It was Barry Nelson. But he isn't the first to play the role of 007 in a movie.Sean Connery, David Niven, Peter Sellers, Barry Nelson... So who is it? I would say if your question is, who is the first to enact JamBo, I would say David Niven and Petter Sellers, but if you just ask me, who is the first James Bond, I'd surely say Barry Nelson.
Feels complicated, doesn't it?