Riddoch was born at
Turriff, in
Aberdeenshire, Scotland, and arrived in Victoria with his parents and family in 1851, settling in
Newtown,
Geelong. He left for the
Ovens River goldfields and was quite successful. He returned to Geelong and set himself up as a storekeeper and wine merchant. In 1861 he purchased Yallum Park Estate, a sheep and cattle station near
Penola. He founded the Coonawarra fruit colony there, and built a grand residence; he was noted for his hospitality. In partnership with his brother, he bought up extensive tracts of land in the South-East of South Australia; by 1891 they owned of pasture and farmland. Their greatest asset,
Glencoe station, founded by
Robert Leake and his brother Edward, covered , and carried 53,000 sheep, 3,500 cattle and 300 horses and featured a magnificent woolshed now held by the National Trust. When the Riddoch brothers dissolved their partnership in 1898, John took the southern end and broke it up for closer settlement; George named his portion "Koorine". ==Politics==