Ivan Julian "Jack" Siedle (11 January 1903 – 24 August 1982) was a South African cricketer who played in 18 Test matches from 1927–28 to 1935–36.

[1] Born on 11 January 1903 in Berea, Durban, Colony of Natal, Siedle was the youngest son of Otto Siedle, who was born in Woolwich, London of southern German stock and who trained as a watchmaker, subsequently emigrating to Durban where he became prominent in the shipping business and public affairs.

A right-hander who played for Natal for 15 seasons from 1922–23 to 1936–37, Jack Siedle bowled occasionally and kept wicket just as infrequently, but his chief value to South Africa was as an opening batsman.

[5] Two matches on, he did better, sharing a partnership of 424 for the first wicket with John Nicolson against Orange Free State which remains the record for the first wicket for Natal and was the record for the whole of first-class cricket in South Africa until January 2020;[6] Nicolson made an unbeaten 252 but Siedle's dismissal for 174 broke the partnership.

[11][12] Three weeks later he almost repeated the feat by making 168 against Yorkshire including 20 fours in what Wisden Cricketers' Almanack described as "an admirable innings".

[18] His overall performance earned praise from Wisden: "Siedle, though a failure in the three Test matches in which he took part, was very consistent otherwise and never looked an easy man of whom to dispose.

[19] Back in South Africa in the 1929–30 season, Siedle hit the highest score of his career in making an unbeaten 265 for Natal in the Currie Cup first-class match against Orange Free State.

[24] Mitchell and Herbie Taylor also scored centuries in the innings and England were forced to follow on, though the match ended as a draw.

[26] And he made 57 and 30 in the final game of the series, also a draw, which left South Africa with a 1–0 series victory; in this match, with the game petering out to a draw, South Africa bowled its part-time bowlers, and Siedle took the only wicket of his entire first-class career, having the England batsman Maurice Turnbull caught and bowled.

[31] Wisden reported that "chief honours" in the match went to Siedle and that his innings was "a great feat in view of the previous poor scoring at headquarters".

It went on: "Siedle, who batted for nearly five hours without giving anything approaching a chance, never took the slightest risk, but some of his off-side strokes and the square and late cuts were perfectly executed.

[33] In the first Test at Nottingham, he top-scored in South Africa's first innings with 59, though he was quickly out for 2 when South Africa were forced to follow on; the first innings was played on a pitch made awkward by weekend rain and Wisden wrote that he played "with commendable skill and steadiness for about three hours" and "afforded emphatic proof of his strength in defence".