Cary was noted for his advocacy and implementation of the Torrens land title system in British Columbia, as well as for his eccentricity and tendency for physical altercations with his political and legal opponents.

He engaged in several ill-fated business ventures, including an unsuccessful purchase of Victoria's water supply and investment into two road construction projects in the rural mainland; one was liquidated after he was accused of illegal land speculation, while the other drew later allegations of biological warfare against the First Nations during the 1862 smallpox epidemic.

He became financially destitute after the construction of his ornate mansion, Cary Castle, and failed investments in the Cariboo Gold Rush.

After his clerk witnessed several bouts of absurd behaviour from Cary in 1865, he was tricked into returning to London via a forged notification that he had been appointed Lord Chancellor.

[2][1] Cairns informed Cary of the recent proposals for the Torrens title system in the Province of South Australia, and advocated that it be implemented in British Columbia.

[1] While the Colony of British Columbia was administered from New Westminster on the Lower Mainland, Cary stayed on Vancouver Island during his service as Attorney General.

In August 1859, the Governor James Douglas appointed Cary as acting attorney general of Vancouver Island, albeit at no additional salary.

[2][1] A week after being appointed acting attorney general in August 1859, Cary announced his candidacy for the 2nd Vancouver Island Legislative Assembly elections the following year.

He ran against Amor de Cosmos, a staunch opponent of Douglas and chief editor of the British Colonist, for the Victoria Town seat.

[6] A long period of legislative discussion resulted in the Land Registry Act 1860, which received royal assent the following January and was implemented throughout 1861.

Cary probably obtained a copy of the draft from a local politician with connections to politics in the Australian colonies; the jurist and future premier John Foster McCreight was a likely candidate, as he had previously practised law in Victoria, Australia.

In 1860, Cary put forward an affidavit alleging that George W. Heaton, the first sheriff of Vancouver Island, had allowed a debtor to escape custody.

On one trip to Lillooet, he was forced to halt at Port Douglas due to worsening eye inflammation (likely iritis) and returned home; this condition would continue to afflict him for the rest of his life.

[1] Cary declined to run in the 1863 Vancouver Island Legislative Assembly elections; he may have considered electoral success unlikely due to his reputation.

[2][1] Cary's hostility towards Amor de Cosmos delayed the passage of his Legal Professions Act, 1865, which allowed lawyers from other British colonies to become members of the Vancouver Island bar.

[2] After being advised by Kennedy that he should resign as Attorney General, Cary wrote to the Executive Council that he was "declining to act any further for the Crown in cases where counsel is required.

In Victoria, he began the construction of an extravagant residence dubbed Cary Castle, overlooking the Strait of Juan de Fuca.

[2][1] In 1862, Cary became a legal advisor and partner to the Bentinck Arm and Fraser River Company, organized for the purpose of building the Bentinck Arm Road, a toll road connecting Bella Coola and the Fraser River, a common route for participants in the Cariboo gold rush.

Edward Graham Alston, another Vancouver Island politician, instead stated that Cary had intended the trip as a money-making opportunity from the outset.

The Executive Council noted a large deficit between the amount of money Cary had received in his duties as registrar and how much had entered the treasury; after he was ordered to pay the difference, he hired Montague Tyrwhitt-Drake as his defence lawyer, although no formal proceedings ever emerged.

His clerk and relative Arthur Stanhope Farwell witnessed him perform eccentric actions, such as sowing crops in a field at midnight by candlelight, speaking nonsense, and collecting bones and mushrooms to produce tooth powder.

[2][1] Cary and his wife had discussed returning to England for several months, although he abruptly changed his mind and announced his plans to move to the Kootenays in early 1865.

A group of acquaintances, including Farwell and Dr. John Sebastian Helmcken, tricked Cary into returning to England, forging a telegram which announced he had been appointed Lord Chancellor at a highly inflated salary.

[1] An obituary published in the British Colonist described Cary as having a "sometimes irritating temperament towards his opponents", but stated that he would have "advanced far beyond most men of his age" were it not for his mental health issues.