David Thomson, 3rd Baron Thomson of Fleet

He was born on June 12, 1957, in Toronto, Ontario, the eldest child of the 2nd Baron Thomson of Fleet and his wife, Marilyn Lavis. He has a sister named Taylor Thomson, and his brother, Peter Thomson, is a race car driver.

In 1978, Thomson received his Bachelor of Arts (subsequently upgraded to an MA (Cantab)) at Selwyn College, Cambridge, where he studied History. As a child, he attended both Upper Canada College and the Hall School.

Thomson started his business career as a junior associate at McLeod Young Weir in Toronto. He left the firm to enter the family business, working in a number of positions in companies controlled by the Thomson family. Thomson was manager of The Bay store at Cloverdale Mall in Etobicoke, and president of Zellers. David Thomson also served as the Chairman of Simpsons (department store) under the Hudson's Bay Company.

Osmington Incorporated

To establish his independence, Thomson founded the real estate firm Osmington Incorporated, which he owned and operated outside of the Thomson empire. Osmington acquires and manages commercial real estate assets on behalf of institutional shareholders, including the Thomson family.

Osmington is part owner of the National Hockey League's Montreal Canadiens and Winnipeg Jets, through its partnership with True North Sports and Entertainment. The company also owns the Canada Life Centre in downtown Winnipeg, Manitoba, and is redeveloping the retail space of Toronto's Union Station. In 2023, Osmington revealed that it was bringing the fast food chain Shake Shack to Canada with plans for 35 outlets. Osmington is also a major investor in FarmersEdge, a precision agriculture company. Thomson's investment activities are managed through Toronto hedge fund Morgan Bay Capital.

According to a plan devised decades ago by Thomson Corporation founder Roy Thomson, when Kenneth Thomson died (in June 2006), control of the family fortune passed on to David:

"David, my grandson, will have to take his part in the running of the Organisation and David's son, too," Roy Thomson wrote in his 1975 autobiography. "With the fortune that we will leave to them go also responsibilities. These Thomson boys that come after Ken are not going to be able, even if they want to, to shrug off these responsibilities."

Following Thomson Reuters' sale of a controlling stake in its financial business in 2018, Thomson expressed frustrations working in the family business. He is currently engaged in discussions with family members to leave the family business, Thomson Reuters, to focus on his own art and real estate activities.

Thomson is the father of seven children from four different mothers. With his first wife, Mary Lou La Prairie, he has two daughters. With his second wife, Laurie Ludwick, Thomson has one son, born after Thomson left the marriage. With the actress Kelly Rowan, Thomson has a daughter, also born after Thomson left the relationship. With his partner Severine Nackers, a former employee of Sotheby's, Thomson has three daughters born between 2015 and 2021. His three youngest children live in Toronto with their father and mother. Thomson was estranged from his eldest daughter, for five years, with her eventually suing her father over mismanagement of the family trusts. The case was settled out of court in 2017.

Thomson is a patron of the Art Gallery of Ontario. Upon the death of his father, he became the 3rd Baron Thomson of Fleet on 12 June 2006, his 49th birthday. He does not use this title in Canada. He is an avid art collector and owns the world's top collection of John Constable.

Thomson has rarely given interviews to the press and maintains a low public profile. "The only substantial interview he has given was to James FitzGerald, who wrote a book about the elite private school (Upper Canada College) they both attended in Toronto", according to a 3 July 2006 article in The New York Times. "In his comments to Mr. FitzGerald 12 years ago, David had little positive to say about many people in the business world". In the interview, Thomson said: "When you try to live a more balanced life, traditional businessmen think that you are not a real man. But who is not the real man? You are telling me? You have not taken a weekend with your wife, you have no spare time that you use constructively, you do not have any hobbies, you do not know how to spell Mozart. And here you are telling me that I am weak?"

Thomson lives in Rosedale, Toronto, in a ravine compound that houses an underground art gallery. The house was previously owned by Toronto architect Raymond Moriyama.