In a 1980 interview with Saturday Night magazine, he spoke of honouring a promise to his father: "In London I'm Lord Thomson; in Toronto I'm Ken.

"[6] At the age of fifty-three, Thomson inherited a media empire of over two-hundred newspaper and television holdings, which also continued to reap profits from a subsidiary North Sea oil investment his father had made a few years earlier.

[3] In 1977, the famously private Thomson suddenly found his collection had become a top news story—from The Globe and Mail in Toronto, to The Times of London—after he’d quietly invited English art forger Tom Keating to come to his office at the top of Thomson Tower and check if any of his cherished Krieghoffs were fakes.

Keating was under investigation by the Art and Antiques squad at Scotland Yard for selling several fake Krieghoffs in the UK, and he claimed to have painted over a hundred of them, mostly in the 1950s.

[3] In November 2002, he announced he would donate in trust around two thousand art works to the Art Gallery of Ontario, including two major acquisitions he had purchased that July: Paul Kane's Scene in the Northwest: Portrait of John Henry Lefroy, at CA$5.1 million, the highest price ever paid for a Canadian painting, and the highlight of his European collection, Peter Paul Rubens' 17th-century masterpiece The Massacre of the Innocents for CA$117 million.

[17][19] The lesser-known European Collection includes an assortment of 17th to 20th century British ship models, a series of Medieval and Baroque ivory carvings, and features the 12th-century Malmesbury châsse, an ornate casket which once held the bones of a Scottish missionary.

In his final years, Thomson lived at 8 Castle Frank Road (gated estate) in the Rosedale area.

Taylor, a one-time actress and film producer, became known for her lawsuit against Christie's auction house, when in 1994 she bought urns supposedly from Louis XV of France that were discovered instead to be 19th century reproductions.