Mumbai: Debutant Keaton Jennings overcame early jitters to score a half century as England made 117-1 on the morning of the opening day of the fourth Test in Mumbai on Thursday.

The South African-born left-hander, who switched allegiance to England to further his international career, endured some nervy opening moments but grew in confidence to sit on 65 not out at the break.

Jennings was almost caught early on and took until the 12th ball to get off the mark but then settled into his groove alongside captain Alastair Cook at the must-win Test.

The pair put on a partnership of 99 with the 24-year-old Jennings striking eight sweet fours during the opening session at Mumbai’s Wankhede Stadium.

Skipper Cook was stumped by wicketkeeper Parthiv Patel shortly before lunch after swinging at a Ravindra Jadeja delivery, for India’s first wicket.

England trail 2-0 in the five-match series and anything less than a victory would see India seal the contest.

Jennings, who was born in Johannesburg and captained the South African under-19 team, was a late call-up for England’s two remaining matches after opener Haseeb Hameed injured his hand during the third Test.

Jennings, whose mother is English, moved to England in 2011 after leaving school, committing himself to four years there so he could become eligible to play for the national side.

Players who were born abroad are eligible to play for England after spending four years playing English county cricket, a policy that has attracted controversy in some quarters.

Number three batsman Joe Root was also at the crease on five.