Although Moffatt began his political career as a leader of the British Tories in Lower Canada, and opposed any conciliatory measures towards the French-Canadians, his views gradually moderated.

After a brief period of studies in London, he emigrated to Lower Canada in 1801 at the age of 14, under the sponsorship of a Montreal merchant, John Ogilvy.

After further studies at William-Henry (now Sorel), he joined Ogilvy's firm, which was part of the XY Company, involved in the fur trade.

Moffatt helped bring stability to the fur trade in Canada by smoothing the way for the merger of the North West Company and the HBC in 1821.

Moffatt's eldest son, Lewis, eventually moved to Toronto, Upper Canada, and opened a successful branch office of the firm.

An inspector for the British parent company reported favourably in 1846 on Moffatt's judgment in assessing risks in Montreal.

[1][2] Outside the partnership, Moffatt also had significant business activities on his own behalf, investing in real estate, settlement in the Eastern Townships, railway construction, mining, and banking.

He also contributed to the political tensions by bringing criminal charges against the editors of two newspapers who had published articles criticising the Legislative Council, Ludger Duvernay and Daniel Tracey.

[4] Moffatt was likely one of the behind-the-scenes originators of a series of venomous anti-French letters which were published in the Montreal Herald in the summer of 1835, opposing the British government's attempts at conciliation with French-Canadians in Lower Canada.

Moffatt and Badgley also met with the newly appointed Governor General of British North America, Lord Durham, and prepared a detailed memorandum for him, giving their views on issues that needed to be addressed in Lower Canada.

[2] Moffatt served in the Legislative Council until 1838, when the constitution of Lower Canada was suspended by a British Act of Parliament, as a result of the Rebellion.

[6][7][8] Durham's tenure as governor general was short, and he was replaced in 1839 by a British member of Parliament, Charles Thomson (later Lord Sydenham).

In a letter to the new Colonial Secretary, Lord Russell, Thomson described Moffatt as "the most pig headed, obstinate, ill tempered brute in the Canadas .

He was successful, defeating Beaubien and returning to Parliament, with Clément-Charles Sabrevois de Bleury as his fellow Montreal member.

[2] During his time in Parliament, Moffatt remained focussed on measures that would help the Montreal English-speaking business community and economy, such as improvements to the harbour.

[2] In fact, the passage of the Rebellion Losses Bill led to Tory riots in Montreal and the burning of the Parliament building.

The repeal had a serious effect on the Canadian economy and led to calls for annexation to the United States by a group of English-speaking Montreal businessmen, traditional Tory supporters.

One of the prominent signers of the Manifesto was John Abbott, a leading lawyer in Montreal and a future prime minister of Canada.

They also passed resolutions calling for a union of the British North American provinces, greater economy in public expenditures, and protectionist measures for Canadian industry.

Moffatt considered that the League had helped to demonstrate that the Conservative and Tory political groupings were not supportive of annexation.

[2] After leaving politics, Moffatt continued his business activities in Montreal, particularly in banking and railways, part of a period of rapid economic changes and development.