On 18 August 1893, at the age of 24, Lee became a professor of Strategy and Tactics, at the Royal Military College of Canada, in Kingston, Ontario,[5] with the local rank of captain.

During the summer of 1897 he was a Special Correspondent for the London Daily Chronicle, covering the earlier stages of the Klondike Gold Rush, based on his travels to Alaska and the Yukon.

[8] Although he would have preferred to have been on active service in South Africa, since the Boer War had just started, Lee enjoyed the challenging diplomatic assignment and became a regular correspondent of Roosevelt.

"[9] Roosevelt also wrote:"Captain Lee, the British attaché, spent some time with us; we had begun to regard him as almost a member of the regiment.

"[10] Later in life Theodore Roosevelt wrote to Rudyard Kipling and told him not to share the contents of the letter with anyone, "except Arthur Lee, to whom you are entirely at liberty to show it.

[15] At the beginning of the First World War Lee served as Lord Kitchener's personal commissioner to report on the Army Medical Services in France, with the rank of temporary colonel.

[1][20] On 8 June 1917, with Lloyd George now Prime Minister, Lee became Director-General of Food Production under Rowland Prothero as President of the Board of Agriculture and Fisheries.

[22] He was elevated to the peerage on 9 July that year as Baron Lee of Fareham, of Chequers in the County of Buckinghamshire,[23] shortly before he resigned as Director-General of Food Production after disagreements with Prothero.

Lee joined the Cabinet and the Privy Council in August 1919[24] when he was appointed Minister of Agriculture and Fisheries, succeeding Prothero.

He became First Lord of the Admiralty on 18 February 1921,[25] and was selected as a second British delegate to attend the Washington Naval Conference, along with Arthur Balfour, later that year.

He resigned from Lloyd George's government in 1922, and was promoted to Viscount Lee of Fareham, of Bridport in the County of Dorset, on 9 December that year.

In 1917, they gave the estate, and the entire contents of the house which included a library, historical papers and manuscripts and a collection of Cromwellian portraits and artefacts, in trust to the nation to be used as the official residence and retreat of successive British Prime Ministers in perpetuity, enabled by the Chequers Estate Act 1917, the first piece of legislation to recognize the figure of a Prime Minister.

The institute, the first to offer degrees in the history of art in Britain, opened in 1932 with William George Constable as its director at Lee's request.

His widow, Viscountess Lee, presented to the Royal Military College of Canada Museum a silver-headed walking stick of her late husband, which he had used daily at RMC fifty-four years earlier.

The stick has two silver bands listing the places where Lee served, or visited, between 1888 and 1904, which include the Royal Military College of Canada.

The third is a photograph of the portrait by Herbert James Gunn in full regalia of a Knight Grand Cross of the Most Honourable Order of the Bath.