He couldn’t resist one last surprise.

Bank of Japan Gov. Haruhiko Kuroda has made his reputation from catching the market off-guard. From his initial "bazookas” of far greater-than-expected monetary easing when he began his term in 2013, to implementing negative rates in 2016 just a week after strenuous denials he was considering anything of the sort, the veteran of central banking knows better than anyone how to pull the rug out from an oblivious market.

Tuesday’s decision to double the trading band of the 10-year Japanese government bond was another master class in timing — and with just two monetary-policy meetings left before his term expires in April — possibly his last. While a move like this was widely expected at some stage, the BOJ governor had been so vociferous in his denials for months now, all 47 economists surveyed by Bloomberg expected nothing — not even the kind of tweak we got. With traders in Japan and overseas either off for the holidays or winding down for the year, a sleepy, sunny December Tuesday was the perfect backdrop for one last rug-pull.