[1] In the early 1800s, Rainy became involved in sugar plantations in the Caribbean which were worked by African slaves in Demerara in Guiana.
Due to extensive family connections he eventually became a full partner in Sandbach, Tinne & Company, a Scottish-run company which dealt in trade in the same field and was prominent in British Guiana, to the extent that the men who ran it were called the "Rothschilds of Demerara" on account of their wealth and influence.
Using monies from the payout to former slave-owners following the Slavery Abolition Act 1833, he purchased the islands of Raasay, Rona and Fladda from Clan MacLeod in 1846: he removed from the land twelve townships of ninety-four Gaelic Highlander families to make way for sheep farming, causing mass depopulation and displacement on the islands.
Among George's siblings were Margaret Rainy (1774—1844), who married to Charles Parker (1771–1828), from a Scottish family in the Colony of Virginia and a major player in Sandbach, Tinne & Company, which ran sugarcane plantations in Demerara, Guiana.
[5] According to the journal of J.C. Cheveley, who visited in 1821, the estates in Demerara containing the slave-worked sugar plantations, were heavily mortgaged to Sandbach, Tinne & Company.
[6][7] Some Scottish newspapers, including, The Sunday Post have claimed that Rainy received the largest payout of all the slave owners.
The last laird, John Macleod, was deep in debt and chose to emigrate to Tasmania having sold Raasay for 35,000 guineas to Rainy.
During this period, with the decline of traditional culture in the Scottish Highlands, many land speculators and landlords moved in to "improve" the estate; the main purpose of this was to clear the native Highland Gaels from the lands, either to urban centres in Great Britain or abroad to North America and Australasia, to make way for sheep farming.
When Rainy came to control Raasay, he set about implementing this process on the island and has been described as "a cruel landlord who epitomised the horror of the Clearances.
[12] Rainy cleared twelve townships of their inhabitants in total to set up sheep farming, with ninety-four Highland Scots families forced from the island, causing mass depopulation and displacement.