Joe Root scored only his second fifty of this Ashes after Australia captured the prize wicket of England captain Alastair Cook on the third day of the fifth and final Test at The Oval on Friday.

England, who at 3-0 up had already won the five-match series, were 97 for one at lunch.

Root was 52 not out, with the only other occasion the 22-year-old Yorkshireman had past fifty this series coming when he made his Test-best 180 in England's crushing 347-run win in the second match at Lord's.

Jonathan Trott was unbeaten on nine.

England, however, were 395 runs behind Australia's first innings 462 for nine declared, a total built on Shane Watson's Test-best 176 and Steven Smith's 138 not out -- his maiden century at this level.

And the hosts needed a further 196 runs to get to a total of 293 that would avoid the follow-on.

On a sunny day promising good overhead conditions for batting on a sound pitch, England made a solid start to their morning's work in a match where victory would see them win four Tests in a home Ashes series for the first time.

Root clipped Ryan Harris off his legs for four while left-hander Cook square-drove the fast bowler for a boundary.

Peter Siddle then saw a good length ball stylish cover-driven to the boundary by Root.

And when left-arm paceman Mitchell Starc, a friend of Root's after playing alongside him at Yorkshire, came on the right-hander clipped him through midwicket for four.

But Cook's mediocre series with the bat continued when, three balls after drinks, he followed a delivery angled across him from Harris, Australia's best bowler of the Ashes, and edged to wicketkeeper Brad Haddin for 25 to end a first-wicket stand worth 68.

It was an all-too familiar exit for Cook in a series where he has scored 243 runs in nine innings with a best of 62 at an average of 27 -- a far cry from his triumphant 2010/11 Ashes tour of Australia where he scored 766 runs at 127.66 with three hundreds.

Cook's exit brought Trott to the crease on the ground where he marked his Test debut with a hundred against Australia in 2009.

Root's pull off Siddle then saw him to a 145-ball fifty with eight fours.