Black Caps star's ton sparks Test win

Kane Williamson has earned an early Christmas present – the New Zealand batsman now officially the world's No.1 ranked batsman.

Williamson guided New Zealand to a series-clinching five-wicket win in the second Test against Sri Lanka in Hamilton today in record-breaking style.

It is Williamson's first trip to the top of the International Cricket Council's Test player rankings in what has been a see-sawing year with Australia skipper Steve Smith, England young gun Joe Root and South Africa superstar AB de Villiers all enjoying stints in the top spot.

Smith will have the chance to push his claim to regain top spot in the Boxing Day and New Year's Tests against the West Indies in Melbourne and Sydney, while De Villiers and Root will be in action when the South Africa v England Test series kicks off in Durban, also on Boxing Day.

Australia's vice-captain David Warner has quickly risen up the rankings and is now the fifth-ranked batsman in the world following a strong summer against New Zealand and the West Indies.

We just thought you might like to see this. Congratulations Kane, it's been a brilliant year for cricket ^MB #NZvSL pic.twitter.com/zvE5cO6pvz — BLACKCAPS (@BLACKCAPS) December 20, 2015

Williamson's unbeaten 108 capped victory as the Black Caps rattled off the 47 runs required on the fourth morning to take a 2-0 series win.

The century took Williamson's 2015 Test aggregate to 1,172 runs, at an average of 90, to beat by eight runs skipper Brendon McCullum's 2014 record for most runs in a calendar year by a New Zealander.

The century was the stylish right-hander's fifth of the year and the 13th of his career. The milestone took him past McCullum's mark for most tons in a year and moved him level with Ross Taylor as joint second most of all time for the Black Caps.

Only Martin Crowe's 17 Test tons are ahead of the pair among New Zealand batsmen.

New Zealand resumed with Williamson on 78, and got himself going with the second ball of the day, turning a delivery from paceman Dushmantha Chameera behind square for four.

There were three more boundaries off Chameera before he brought up his century with another four off the same bowler through square leg.

Most Test runs by NZ batsman in a calendar year