New Zealand maestro Kane Williamson crafts innings of 238 against Pakistan as sublime summer rolls on

Less than a week after pocketing the International Cricket Council's number-one rank in men's Test batting New Zealand supremo Kane Williamson has again crafted a masterful innings.

The elegant right-hander today notched his second double century of New Zealand's summer, compiling 238 runs against Pakistan in Christchurch.

Williamson took 327 balls to reach the fourth double ton of his Test career, whipping a Shaheen Shah Afridi delivery into a gap between mid-wicket and mid-on and celebrating in his typically understated fashion.

Shortly after the 83-Test Black Cap was dismissed by Faheem Ashraf, New Zealand declared on 6-659, streaks ahead of Pakistan's first-innings total of 297 all out.

Williamson has now amassed 639 runs at an average of 159.75 across three Tests this summer, including knocks of 251, 238 and 129, in matches against the West Indies and Pakistan.

Spark Sport commentator and former New Zealand all-rounder Grant Elliott praised Williamson's temperament.

"It's the way he goes about his work: the concentration levels, the focus," Grant said.

"He would have been just short of 10 hours at the crease. I don't even sleep for 10 hours.

"Fantastic innings. (Scored) 238 and he was looking at one stage at a triple (hundred)."

Fellow Spark Sport commentator and former New Zealand batsman Craig McMillan said it was Williamson at his vintage best.

"We've seen a lot of this during this summer, haven't we?" McMillan said.

"He manipulates the field, gets the fielders in the positions he wants and then he just goes about scoring runs. Both sides of the wicket, front foot, back foot, cutting.

"Whatever he needs to do - he's just a run machine and he is so good to watch."

Making Williamson's phenomenal summer even more special is the fact he scored his first two centuries - his 251 and 129 - on incredibly green wickets.

Spark Sport commentator and former White Ferns batsman Frankie McKay said "the bowlers will be licking their lips", but instead it was Williamson licking his lips on his way to the top Test score of his career.

The Black Caps' skipper was last week named at first drop in the ICC's men's Test team of the decade.

He joined batsmen Alastair Cook, David Warner, Virat Kohli, Steve Smith and Kumar Sangakkara in the star-studded side, while all-rounder Ben Stokes and bowlers Ravichandran Ashwin, Dale Steyn, Stuart Broad and James Anderson rounded out the XI.

Williamson has now scored 7115 Test runs, making him the third-highest run-scorer in New Zealand history behind Ross Taylor (7379) and Stephen Fleming (7172).

But 30-year-old Williamson likely has a number of years left in his Test career and has a higher Test average than both Taylor and Fleming.

In today's innings of 238, he reached 7000 Test runs and his average surpassed those of Kohli and Sachin Tendulkar.