England have set-up a Test shootout for the role of Alastair Cook's Test opening partner as four batsmen vie for the opportunity in the Lions squad which will face South Africa in Canterbury next week. Haseeb Hameed and Keaton Jennings are the two men in pole position, but they will have to promote their claims alongside the Middlesex batsman Nick Gubbins and Mark Stoneman, who is having a fine inaugural season with Surrey since making the switch from Durham.

Jennings is averaging a shade under 40, with only one century, in a Durham side that has been in the doldrums since relegation to Division Two of the Specsavers Championship with a 48-point penalty, but he also had an unproductive Lions tour of Sri Lanka earlier this year as he also came to terms with the responsibilities of captaincy, a role he has retained.

Hameed has had a disturbing loss of form, averaging only 19.33 and still to pass fifty in six Championship matches for Lancashire as his inclusion in their 50-over side has coincided with a reduction in the ingrained concentration that won so many plaudits last season.

The confidence surrounding England's one-day side as they have advanced to the semi-final of the Champions Trophy has not been without its own uncertainty about the top of the order with Jonny Bairstow well placed to replace the out-of-form Jason Roy in the semi-final against Pakistan on Wednesday.

The questions in the Test side ahead of a four-match series against South Africa, beginning at Lord's on July 6, are equally pressing, yet with different personnel. Joe Root batted at No. 3 throughout England's disastrous Test series in India last winter, which if that policy persisted against South Africa, and ahead of this winter's Ashes series, would leave only a single place available.

Somerset's spin-bowling duo, Jack Leach and Dom Bess, a teenaged offspinner, are both named in the squad. Leach, who played in the Lions' last four-day game against Sri Lanka A in Dambulla in February, is also joined by another Somerset team-mate in Jamie Overton.

Stoneman and Bess, about a decade apart in age, are the only two members of the squad not to have played previously for the Lions. A separate Lions squad will be named next week for a three-day match against the senior South Africa tourists in Worcester starting on June 29.

James Whitaker, the national selector, said: "We have had to delay naming that squad because the game clashes with the Royal London One-Day Cup final, and we will not consider players from the counties who qualify for Lord's.

"There were other considerations in selecting this squad - as ever, we were mindful of counties who have important fixtures in the Specsavers County Championship, while four members of the Lions squad who won the Royal London One-Day Series against South Africa A were unavailable after being selected for the full England squad for the NatWest T20 internationals against South Africa."

England Lions squad: Keaton Jennings (Durham, capt), Mark Stoneman (Surrey), Haseeb Hameed (Lancashire), Nick Gubbins (Middlesex), Dan Lawrence (Essex), Ben Foakes (Surrey, wk), Sam Curran (Surrey), Jamie Overton (Somerset), Tom Helm (Middlesex), Jamie Porter (Essex), George Garton (Sussex), Jack Leach (Somerset), Dominic Bess (Somerset)