We will recall that one of Le Carré's sons, no less, hinted to the Radio Times (owned by a BBC company) that a second series was in the offing: http://www.radiotimes.com/news/2016-03-05/bbc-in-talks-about-a-second-series-of-tom-hiddleston-and-hugh-laurie-drama-the-night-manager

Then TH and HL said no it DEFINITELY wasn't.

Apparently HL has been taken aside by the money men at the AMC and told to shut it in case the world wants more naked Hiddles: http://www.ibtimes.co.uk/hugh-laurie-contradicts-tom-hiddleston-night-manager-second-series-possible-1555434